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margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">Android's use of safe-by-design principles drives our adoption of memory-safe languages like Rust, making exploitation of the OS increasingly difficult with every release. To provide a secure foundation, we’re extending hardening and the use of </span><a href="https://security.googleblog.com/2023/10/bare-metal-rust-in-android.html" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">memory-safe languages to low-level firmware</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> (including in </span><a href="https://cs.android.com/android/platform/superproject/main/+/main:trusty/user/app/keymint/lib.rs;drc=4176f2465d7dc81c398730cb579c0a4949a9a832" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">Trusty apps</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">).</span></p><br /><p dir="ltr" style="line-height: 1.3800000000000001; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">In this blog post, we'll show you how to gradually introduce </span><a href="https://security.googleblog.com/2021/04/rust-in-android-platform.html#:~:text=But%20what%20about%20all%20that%20existing%20C%2B%2B%3F" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">Rust into your existing firmware</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">, prioritizing new code and the most security-critical code. You'll see how easy it is to boost security with drop-in Rust replacements, and we'll even demonstrate how the Rust toolchain can handle specialized bare-metal targets.</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">Drop-in Rust replacements for C code are not a novel idea and have been used in other cases, such as </span><a href="https://mail.gnome.org/archives/desktop-devel-list/2017-January/msg00001.html" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">librsvg’s adoption of Rust</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> which involved </span><a href="https://web.archive.org/web/20170928062853/https://people.gnome.org/~federico/blog/docs/fmq-porting-c-to-rust.pdf" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">replacing C functions with Rust functions</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> in-place. We seek to demonstrate that this approach is viable for firmware, providing a path to memory-safety in an efficient and effective manner.</span></p><h1 dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 20pt;"><span style="font-family: Arial, sans-serif; font-size: 20pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; font-weight: 400; vertical-align: baseline; white-space-collapse: preserve;">Memory Safety for Firmware</span></h1><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">Firmware serves as the interface between hardware and higher-level software. Due to the lack of software security mechanisms that are standard in higher-level software, vulnerabilities in firmware code can be dangerously exploited by malicious actors. Modern phones contain many coprocessors responsible for handling various operations, and each of these run their own firmware. Often, firmware consists of large legacy code bases written in memory-unsafe languages such as C or C++. Memory unsafety is the leading cause of vulnerabilities in </span><a href="https://source.android.com/docs/security/test/memory-safety" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">Android</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">, </span><a href="https://www.chromium.org/Home/chromium-security/memory-safety/" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">Chrome</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">, and many other code bases.</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">Rust provides a memory-safe alternative to C and C++ with comparable performance and code size. Additionally it supports interoperability with C with no overhead. The Android team has discussed </span><a href="https://security.googleblog.com/2023/10/bare-metal-rust-in-android.html" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">Rust for bare-metal firmware previously</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">, and has </span><a href="https://google.github.io/comprehensive-rust/bare-metal.html" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">developed training specifically for this domain</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">.</span></p><h1 dir="ltr" style="line-height: 1.38; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial, sans-serif; font-size: 20pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; font-weight: 400; vertical-align: baseline; white-space-collapse: preserve;">Incremental Rust Adoption</span></h1><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">Our incremental approach focusing on replacing new and highest risk existing code (for example, code which processes external untrusted input) can provide maximum security benefits with the least amount of effort. Simply writing any new code in Rust reduces the number of new vulnerabilities and over time can lead to a reduction in </span><a href="https://security.googleblog.com/2021/04/rust-in-android-platform.html" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">the number of outstanding vulnerabilities</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">.</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">You can replace existing C functionality by writing a thin Rust shim that translates between an existing Rust API and the C API the codebase expects. The C API is replicated and exported by the shim for the existing codebase to link against. The shim serves as </span><a href="https://doc.rust-lang.org/nomicon/ffi.html#calling-rust-code-from-c" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">a wrapper</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> around the Rust library API, bridging the existing C API and the Rust API. This is a common approach when rewriting or replacing existing libraries with a Rust alternative.</span></p><h1 dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 20pt;"><span style="font-family: Arial, sans-serif; font-size: 20pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; font-weight: 400; vertical-align: baseline; white-space-collapse: preserve;">Challenges and Considerations</span></h1><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">There are several challenges you need to consider before introducing Rust to your firmware codebase. In the following section we address the general state of </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">no_std</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> Rust (that is, bare-metal Rust code), how to find the right off-the-shelf crate (a rust library), porting an std crate to </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">no_std</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">, using Bindgen to produce FFI bindings, how to approach allocators and panics, and how to set up your toolchain.</span></p><h2 dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 18pt;"><span style="font-family: Arial, sans-serif; font-size: 16pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; font-weight: 400; vertical-align: baseline; white-space-collapse: preserve;">The Rust Standard Library and Bare-Metal Environments</span></h2><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">Rust's standard library consists of three crates: </span><a href="https://doc.rust-lang.org/core/" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">core</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">, </span><a href="https://doc.rust-lang.org/alloc/" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">alloc</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">, and </span><a href="https://doc.rust-lang.org/std/" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">std</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">. The </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">core</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> crate is always available. The </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">alloc</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> crate requires an allocator for its functionality. The </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">std</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> crate assumes a full-blown operating system and is commonly not supported in bare-metal environments. A third-party crate indicates it doesn’t rely on </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">std</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> through the crate-level </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">#![no_std] </span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">attribute. This crate is said to be </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">no_std</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> compatible. The rest of the blog will focus on these.</span></p><h2 dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 18pt;"><span style="font-family: Arial, sans-serif; font-size: 16pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; font-weight: 400; vertical-align: baseline; white-space-collapse: preserve;">Choosing a Component to Replace</span></h2><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">When choosing a component to replace, focus on self-contained components with robust testing. Ideally, the components functionality can be provided by an open-source implementation readily available which supports bare-metal environments.</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">Parsers which handle standard and commonly used data formats or protocols (such as, XML or DNS) are good initial candidates. This ensures the initial effort focuses on the challenges of integrating Rust with the existing code base and build system rather than the particulars of a complex component and simplifies testing. This approach eases introducing more Rust later on.</span></p><h2 dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 18pt;"><span style="font-family: Arial, sans-serif; font-size: 16pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; font-weight: 400; vertical-align: baseline; white-space-collapse: preserve;">Choosing a Pre-Existing Crate (Rust Library)</span></h2><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">Picking the right open-source crate (Rust library) to replace the chosen component is crucial. Things to consider are:</span></p><ul style="margin-bottom: 0; margin-top: 0; padding-inline-start: 48px;"><li aria-level="1" dir="ltr" style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; list-style-type: disc; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">Is the crate well maintained, for example, are open issues being addressed and does it use recent crate versions?</span></p></li><li aria-level="1" dir="ltr" style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; list-style-type: disc; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">How widely used is the crate? This may be used as a quality signal, but also important to consider in the context of using crates later on which may depend on it.</span></p></li><li aria-level="1" dir="ltr" style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; list-style-type: disc; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">Does the crate have acceptable documentation?</span></p></li><li aria-level="1" dir="ltr" style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; list-style-type: disc; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">Does it have acceptable test coverage?</span></p></li></ul><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">Additionally, the crate should ideally be </span><span style="color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">no_std</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> compatible, meaning the standard library is either unused or can be disabled. While a wide range of </span><span style="color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">no_std</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> compatible crates exist, others do not yet support this mode of operation – in those cases, see the next section on converting a </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">std</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> library to </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">no_std</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">.</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 10pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">By convention, crates which optionally support </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">no_std</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> will provide an </span><span style="color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">std</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> feature to indicate whether the standard library should be used. Similarly, the </span><span style="color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">alloc</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> feature usually indicates using an allocator is optional.</span></p><br /><div align="left" dir="ltr" style="margin-left: -14.25pt;"><table style="border-collapse: collapse; border: none;"><colgroup><col width="67"></col><col width="790"></col></colgroup><tbody><tr style="height: 54.75pt;"><td style="background-color: #e1f5fe; overflow-wrap: break-word; overflow: hidden; padding: 14.4pt 14.4pt 14.4pt 14.4pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #01579b; font-family: Roboto, sans-serif; font-size: 12pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"><span style="border: none; display: inline-block; height: 40px; overflow: hidden; width: 40px;"><img height="40" src="https://lh7-rt.googleusercontent.com/docsz/AD_4nXfPgBmsZj6ZTOto6Frw_NToC18UKVimJ8SHuCerE7W01D83L3qeJ-Qop83lTf1pvDshgc4CW3pap9aXpzVpSQZtG9EVZDzIQKD5x3vZ4yiEGDxMODTUTNZtlGMVy3Sh-I1i4x-QY8RzBAaqOSap6rGuC9WYg4pdhUO5vY_-OqUCcPssnZAYmUKb-FnV5Ainemg?key=NlrS0k5AvJIpHEA9_mIwTQ" style="margin-left: 0px; margin-top: 0px;" width="40" /></span></span></p></td><td style="background-color: #e1f5fe; overflow-wrap: break-word; overflow: hidden; padding: 14.4pt 14.4pt 14.4pt 14.4pt; vertical-align: middle;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #01579b; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; font-weight: 700; vertical-align: baseline; white-space-collapse: preserve;">Note:</span><span style="background-color: transparent; color: #01579b; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> Even when a library declares </span><span style="background-color: transparent; color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">#![no_std] </span><span style="background-color: transparent; color: #01579b; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">in its source, there is no guarantee that its dependencies don’t depend on </span><span style="background-color: transparent; color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">std</span><span style="background-color: transparent; color: #01579b; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">. We recommend looking through the dependency tree to ensure that all dependencies support </span><span style="background-color: transparent; color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">no_std</span><span style="background-color: transparent; color: #01579b; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">, or test whether the library compiles for a </span><span style="background-color: transparent; color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">no_std</span><span style="background-color: transparent; color: #01579b; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> target. The only way to know is currently by trying to compile the crate for a bare-metal target.</span></p></td></tr></tbody></table></div><br /><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 10pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">For example, one approach is to run </span><span style="color: #0f9d58; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">cargo check</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> with a bare-metal toolchain provided through </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">rustup</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">:</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #188038; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">$ rustup target add aarch64-unknown-none</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #188038; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">$ cargo check</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #188038; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">--target</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #188038; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">aarch64-unknown-none --no-default-features</span></p><br /><h2 dir="ltr" style="line-height: 1.38; margin-bottom: 10pt; margin-top: 14pt;"><span style="font-family: "Google Sans", sans-serif; font-size: 16pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; font-weight: 400; vertical-align: baseline; white-space-collapse: preserve;">Porting a </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 16pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; font-weight: 400; vertical-align: baseline; white-space-collapse: preserve;">std</span><span style="font-family: "Google Sans", sans-serif; font-size: 16pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; font-weight: 400; vertical-align: baseline; white-space-collapse: preserve;"> Library to </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 16pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; font-weight: 400; vertical-align: baseline; white-space-collapse: preserve;">no_std</span></h2><p dir="ltr" style="line-height: 1.38; margin-bottom: 10pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">If a library does not support </span><span style="color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">no_std</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">, it might still be possible to port it to a bare-metal environment – especially file format parsers and other OS agnostic workloads. Higher-level functionality such as file handling, threading, and async code may present more of a challenge. In those cases, such functionality can be hidden behind feature flags to still provide the core functionality in a </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">no_std</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> build.</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 10pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">To port a </span><span style="color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">std</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> crate to </span><span style="color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">no_std</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> (</span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">core</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">+</span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">alloc</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">):</span></p><ul style="margin-bottom: 0; margin-top: 0; padding-inline-start: 48px;"><li aria-level="1" dir="ltr" style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; list-style-type: disc; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">In the </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">cargo.toml</span><span style="font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;"> file, add a </span><span style="color: #0d904f; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">std</span><span style="font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;"> feature, then add this </span><span style="color: #0d904f; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">std</span><span style="font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;"> feature to the </span><span style="color: #0d904f; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">default </span><span style="font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">features</span></p></li><li aria-level="1" dir="ltr" style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; list-style-type: disc; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="line-height: 1.38; margin-bottom: 10pt; margin-top: 0pt;"><span style="font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">Add the following lines to the top of the </span><span style="color: #0d904f; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">lib.rs</span><span style="font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">:</span></p></li></ul><div align="left" dir="ltr" style="margin-left: 0pt;"><table style="border-collapse: collapse; border: none;"><colgroup></colgroup><tbody><tr style="height: 0pt;"><td style="background-color: #fafafa; border-bottom: solid #e0e0e0 1pt; border-left: solid #e0e0e0 1pt; border-right: solid #e0e0e0 1pt; border-top: solid #e0e0e0 1pt; overflow-wrap: break-word; overflow: hidden; padding: 5pt 5pt 5pt 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #455a64; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">#![no_std]</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #455a64; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">#[cfg(feature = "std")]</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #9c27b0; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">extern</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> crate std</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">;</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #9c27b0; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">extern</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> crate alloc</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">;</span></p></td></tr></tbody></table></div><p dir="ltr" style="line-height: 1.38; margin-bottom: 10pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">Then, iteratively fix all occurring compiler errors as follows:</span></p><ol style="margin-bottom: 0; margin-top: 0; padding-inline-start: 48px;"><li aria-level="1" dir="ltr" style="font-family: "Google Sans", sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; list-style-type: lower-alpha; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">Move any </span><span style="color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">use</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;"> directives from </span><span style="color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">std</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;"> to either </span><span style="color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">core</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;"> or </span><span style="color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">alloc</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">.</span></p></li><li aria-level="1" dir="ltr" style="font-family: "Google Sans", sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; list-style-type: lower-alpha; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">Add </span><span style="color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">use</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;"> directives for all types that would otherwise automatically be imported by the </span><a href="https://doc.rust-lang.org/std/prelude/index.html" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; text-wrap: wrap; vertical-align: baseline;">std prelude</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">, such as </span><span style="color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">alloc::vec::Vec</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;"> and</span><span style="color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;"> alloc::string::String</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">.</span></p></li><li aria-level="1" dir="ltr" style="font-family: "Google Sans", sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; list-style-type: lower-alpha; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">Hide anything that doesn't exist in </span><span style="color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">core</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;"> or </span><span style="color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">alloc</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;"> and cannot otherwise be supported in the </span><span style="color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">no_std</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;"> build (such as file system accesses) behind a </span><span style="color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">#[cfg(feature = </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">"</span><span style="color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">std</span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">"</span><span style="color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">)] </span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">guard.</span></p></li><li aria-level="1" dir="ltr" style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; list-style-type: lower-alpha; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">Anything that needs to interact with the embedded environment may need to be explicitly handled, such as functions for I/O. These likely need to be behind a </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">#[cfg(not(feature = "std"))]</span><span style="font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;"> guard.</span></p></li><li aria-level="1" dir="ltr" style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; list-style-type: lower-alpha; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="line-height: 1.38; margin-bottom: 10pt; margin-top: 0pt;"><span style="font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">Disable </span><span style="color: #0d904f; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">std</span><span style="font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;"> for all dependencies (that is, change their definitions in </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">Cargo.toml</span><span style="font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">, if using Cargo).</span></p></li></ol><p dir="ltr" style="line-height: 1.38; margin-bottom: 10pt; margin-top: 0pt;"><span style="font-family: "Google Sans", sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">This needs to be repeated for all dependencies within the crate dependency tree that do not support </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">no_std</span><span style="font-family: "Google Sans", sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> yet.</span></p><h1 dir="ltr" style="line-height: 1.38; margin-bottom: 10pt; margin-top: 20pt;"><span style="font-family: Arial, sans-serif; font-size: 20pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; font-weight: 400; vertical-align: baseline; white-space-collapse: preserve;">Custom Target Architectures</span></h1><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">There are a number of officially </span><a href="https://doc.rust-lang.org/rustc/platform-support.html" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">supported targets</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> by the Rust compiler, however, many bare-metal targets are missing from that list. Thankfully, the Rust compiler lowers to LLVM IR and uses an internal copy of LLVM to lower to machine code. Thus, it can support any target architecture that LLVM supports by defining a custom target.</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">Defining a custom target requires a toolchain built with the </span><a href="https://github.com/rust-lang/rust/blob/master/config.example.toml#L577-L580" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">channel set to dev or nightly</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">. Rust’s </span><a href="https://docs.rust-embedded.org/embedonomicon/custom-target.html" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">Embedonomicon</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> has a wealth of information on this subject and should be referred to as the source of truth. </span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">To give a quick overview, a custom target JSON file can be constructed by finding a similar supported target and dumping the JSON representation:</span></p><br /><div align="left" dir="ltr" style="margin-left: 0pt;"><table style="border-collapse: collapse; border: none;"><colgroup></colgroup><tbody><tr style="height: 0pt;"><td style="background-color: #fafafa; border-bottom: solid #e0e0e0 1pt; border-left: solid #e0e0e0 1pt; border-right: solid #e0e0e0 1pt; border-top: solid #e0e0e0 1pt; overflow-wrap: break-word; overflow: hidden; padding: 5pt 5pt 5pt 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">$ rustc </span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">--</span><span style="background-color: transparent; color: #9c27b0; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">print</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> target</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">-</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">list</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">[...]</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">armv7a</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">-</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">none</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">-</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">eabi</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">[...]</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">$ rustc </span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">-</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">Z unstable</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">-</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">options </span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">--</span><span style="background-color: transparent; color: #9c27b0; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">print</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> target</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">-</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">spec</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">-</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">json </span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">--</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">target armv7a</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">-</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">none</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">-</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">eabi</span></p></td></tr></tbody></table></div><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">This will print out a target JSON that looks something like:</span></p><div align="left" dir="ltr" style="margin-left: 0pt;"><table style="border-collapse: collapse; border: none;"><colgroup></colgroup><tbody><tr style="height: 0pt;"><td style="background-color: #fafafa; border-bottom: solid #e0e0e0 1pt; border-left: solid #e0e0e0 1pt; border-right: solid #e0e0e0 1pt; border-top: solid #e0e0e0 1pt; overflow-wrap: break-word; overflow: hidden; padding: 5pt 5pt 5pt 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">$ rustc </span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">--</span><span style="background-color: transparent; color: #9c27b0; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">print</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> target</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">-</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">spec</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">-</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">json </span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">-</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">Z unstable</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">-</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">options </span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">--</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">target</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">=</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">armv7a</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">-</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">none</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">-</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">eabi</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">{</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">  </span><span style="background-color: transparent; color: #0f9d58; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">"abi"</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">:</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="background-color: transparent; color: #0f9d58; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">"eabi"</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">,</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">  </span><span style="background-color: transparent; color: #0f9d58; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">"arch"</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">:</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="background-color: transparent; color: #0f9d58; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">"arm"</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">,</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">  </span><span style="background-color: transparent; color: #0f9d58; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">"c-enum-min-bits"</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">:</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="background-color: transparent; color: #c53929; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">8</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">,</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">  </span><span style="background-color: transparent; color: #0f9d58; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">"crt-objects-fallback"</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">:</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="background-color: transparent; color: #0f9d58; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">"false"</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">,</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">  </span><span style="background-color: transparent; color: #0f9d58; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">"data-layout"</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">:</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="background-color: transparent; color: #0f9d58; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">"e-m:e-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64"</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">,</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">  </span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">[...]</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">}</span></p></td></tr></tbody></table></div><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">This output can provide a starting point for defining your target. Of particular note, the data-layout field is defined in the </span><a href="https://llvm.org/docs/LangRef.html#data-layout" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">LLVM documentation</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">.</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">Once the target is defined, </span><span style="color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">libcore</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> and </span><span style="color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">liballoc</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> (and </span><span style="color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">libstd</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">, if applicable) must be built from source for the newly defined target. If using Cargo, building with </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">-Z build-std</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> accomplishes this, indicating that these libraries should be built from source for your target along with your crate module:</span></p><div align="left" dir="ltr" style="margin-left: 0pt;"><table style="border-collapse: collapse; border: none;"><colgroup></colgroup><tbody><tr style="height: 0pt;"><td style="background-color: #fafafa; border-bottom: solid #e0e0e0 1pt; border-left: solid #e0e0e0 1pt; border-right: solid #e0e0e0 1pt; border-top: solid #e0e0e0 1pt; overflow-wrap: break-word; overflow: hidden; padding: 5pt 5pt 5pt 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #455a64; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"># set build-std to the list of libraries needed</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">cargo build </span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">-</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">Z build</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">-</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">std</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">=</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">core</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">,</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">alloc </span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">--</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">target my_target</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">.</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">json</span></p></td></tr></tbody></table></div><h2 dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 18pt;"><span style="font-family: Arial, sans-serif; font-size: 16pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; font-weight: 400; vertical-align: baseline; white-space-collapse: preserve;">Building Rust With LLVM Prebuilts</span></h2><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">If the bare-metal architecture is not supported by the LLVM bundled internal to the Rust toolchain, a custom Rust toolchain can be produced with any LLVM prebuilts that support the target.</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">The instructions for building a Rust toolchain can be found in detail in the </span><a href="https://rustc-dev-guide.rust-lang.org/building/how-to-build-and-run.html" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">Rust Compiler Developer Guide</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">. In the </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">config.toml</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">, </span><a href="https://github.com/rust-lang/rust/blob/036b38ced36b0ed16579f95b4647ba7424f6b1bc/config.example.toml#L790-L793" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">llvm-config</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> must be set to the path of the LLVM prebuilts.</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">You can find the latest Rust Toolchain supported by a particular version of LLVM by checking the </span><a href="https://github.com/rust-lang/rust/blob/master/RELEASES.md" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">release notes</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> and looking for releases which bump up the minimum supported LLVM version. For example, Rust </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">1.76</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> bumped the </span><a href="https://github.com/rust-lang/rust/blob/master/RELEASES.md" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">minimum LLVM to 16</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> and </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">1.73</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> bumped the </span><a href="https://github.com/rust-lang/rust/blob/master/RELEASES.md" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">minimum LLVM to 15</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">. That means with LLVM15 prebuilts, the latest Rust toolchain that can be built is </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">1.75</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">.</span></p><h1 dir="ltr" style="line-height: 1.38; margin-bottom: 10pt; margin-top: 20pt;"><span style="font-family: Arial, sans-serif; font-size: 20pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; font-weight: 400; vertical-align: baseline; white-space-collapse: preserve;">Creating a Drop-In Rust Shim</span></h1><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">To create a drop-in replacement for the C/C++ function or API being replaced, the shim needs two things: it must provide the same API as the replaced library and it must know how to run in the firmware’s bare-metal environment.</span></p><h2 dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 18pt;"><span style="font-family: Arial, sans-serif; font-size: 16pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; font-weight: 400; vertical-align: baseline; white-space-collapse: preserve;">Exposing the Same API</span></h2><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">The first is achieved by defining a Rust FFI interface with the same function signatures.</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">We try to keep the amount of unsafe Rust as minimal as possible by putting the actual implementation in a safe function and exposing a thin wrapper type around.</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">For example, the FreeRTOS </span><a href="https://github.com/FreeRTOS/coreJSON?tab=readme-ov-file#reference-example" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">coreJSON example</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> includes a </span><a href="https://github.com/FreeRTOS/coreJSON/blob/9ebaeb55cce39a6f79da9cceaa0cbc664a462c8b/source/include/core_json.h#L101-L102" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">JSON_Validate</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> C function with the following signature:</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">JSONStatus_t</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">JSON_Validate(</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">const</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #9334e6; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">char</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">*</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">buf,</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">size_t</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">max</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">);</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">We can write a shim in Rust between it and the memory safe </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">serde_json</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> crate to expose the C function signature. We try to keep the unsafe code to a minimum and call through to a safe function early:</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">#[no_mangle]</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">pub</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">unsafe</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #1967d2; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">extern</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #188038; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">"C"</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">fn</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">JSON_Validate(buf:</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">*const</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">c_char,</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">len:</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">usize)</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">-></span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">JSONStatus_t</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">{</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">    </span><span style="color: #1967d2; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">if</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">buf.is_null()</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">{</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">        </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">JSONStatus::JSONNullParameter</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">as</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">_</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">    </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">}</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #1967d2; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">else</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #1967d2; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">if</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">len</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">==</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #c5221f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">0</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">{</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">        </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">JSONStatus::JSONBadParameter</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">as</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">_</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">    </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">}</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #1967d2; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">else</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">{</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">        </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">json_validate(slice_from_raw_parts(buf</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">as</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">_,</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">len).as_ref().unwrap())</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">as</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">_</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">    </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">}</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">}</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #b80672; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">// No more unsafe code in here.</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">fn</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">json_validate(buf:</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">&[u8])</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">-></span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">JSONStatus</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">{</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">    </span><span style="color: #1967d2; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">if</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">serde_json::from_slice::<Value>(buf).is_ok()</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">{</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">        </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">JSONStatus::JSONSuccess</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">    </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">}</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #1967d2; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">else</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">{</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">        </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">ILLEGAL_DOC</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">    </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">}</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">}</span></p><br /><br /><div align="left" dir="ltr" style="margin-left: -16.5pt;"><table style="border-collapse: collapse; border: none;"><colgroup><col width="70"></col><col width="905"></col></colgroup><tbody><tr style="height: 54.75pt;"><td style="background-color: #e1f5fe; overflow-wrap: break-word; overflow: hidden; padding: 14.4pt 14.4pt 14.4pt 14.4pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #01579b; font-family: Roboto, sans-serif; font-size: 12pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"><span style="border: none; display: inline-block; height: 24px; overflow: hidden; width: 24px;"><img height="24" src="https://lh7-rt.googleusercontent.com/docsz/AD_4nXfPgBmsZj6ZTOto6Frw_NToC18UKVimJ8SHuCerE7W01D83L3qeJ-Qop83lTf1pvDshgc4CW3pap9aXpzVpSQZtG9EVZDzIQKD5x3vZ4yiEGDxMODTUTNZtlGMVy3Sh-I1i4x-QY8RzBAaqOSap6rGuC9WYg4pdhUO5vY_-OqUCcPssnZAYmUKb-FnV5Ainemg?key=NlrS0k5AvJIpHEA9_mIwTQ" style="margin-left: 0px; margin-top: 0px;" width="24" /></span></span></p></td><td style="background-color: #e1f5fe; overflow-wrap: break-word; overflow: hidden; padding: 14.4pt 14.4pt 14.4pt 14.4pt; vertical-align: middle;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #01579b; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; font-weight: 700; vertical-align: baseline; white-space-collapse: preserve;">Note:</span><span style="background-color: transparent; color: #01579b; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> This is a very simple example. For a highly resource constrained target, you can avoid </span><span style="background-color: transparent; color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">alloc</span><span style="background-color: transparent; color: #01579b; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> and use </span><a href="https://docs.rs/serde-json-core/latest/serde_json_core" style="text-decoration-line: none;"><span style="background-color: transparent; color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">serde_json_core</span></a><span style="background-color: transparent; color: #01579b; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">, which has even lower overhead but requires pre-defining the JSON structure so it can be allocated on the stack.</span></p></td></tr></tbody></table></div><br /><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">For further details on how to create an FFI interface, </span><a href="https://doc.rust-lang.org/nomicon/ffi.html" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">the Rustinomicon covers this topic extensively</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">.</span></p><h2 dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 18pt;"><span style="font-family: Arial, sans-serif; font-size: 16pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; font-weight: 400; vertical-align: baseline; white-space-collapse: preserve;">Calling Back to C/C++ Code</span></h2><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">In order for any Rust component to be functional within a C-based firmware, it will need to call back into the C code for things such as allocations or logging. Thankfully, there are a variety of tools available which automatically generate Rust FFI bindings to C. That way, C functions can easily be invoked from Rust.</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">The standard means of doing this is with the </span><a href="https://github.com/rust-lang/rust-bindgen" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">Bindgen</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> tool. You can use Bindgen to parse all relevant C headers that define the functions Rust needs to call into. It's important to invoke Bindgen with the same </span><span style="color: #0f9d58; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">CFLAGS</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> as the code in question is built with, to ensure that the bindings are generated correctly.</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">Experimental support for producing </span><a href="https://github.com/rust-lang/rust-bindgen/discussions/2405" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">bindings to static inline functions</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> is also available.</span></p><h2 dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 18pt;"><span style="font-family: Arial, sans-serif; font-size: 16pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; font-weight: 400; vertical-align: baseline; white-space-collapse: preserve;">Hooking Up The Firmware’s Bare-Metal Environment</span></h2><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">Next we need to hook up Rust panic handlers, global allocators, and critical section handlers to the existing code base. This requires producing definitions for each of these which call into the existing firmware C functions.</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">The Rust panic handler must be defined to handle unexpected states or failed assertions. A custom panic handler can be defined via the </span><a href="https://doc.rust-lang.org/nomicon/panic-handler.html" style="text-decoration-line: none;"><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">panic_handler</span><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;"> attribute</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">. This is specific to the target and should, in most cases, either point to an abort function for the current task/process, or a panic function provided by the environment.</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">If an allocator is available in the firmware and the crate relies on the </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">alloc</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> crate, the Rust allocator can be hooked up by </span><a href="https://doc.rust-lang.org/stable/core/alloc/trait.GlobalAlloc.html" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">defining a global allocator implementing GlobalAlloc</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">.</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">If the crate in question relies on concurrency, critical sections will need to be handled. Rust's </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">core</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> or </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">alloc</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> crates do not directly provide a means for defining this, however the </span><a href="https://docs.rs/critical-section/latest/critical_section/" style="text-decoration-line: none;"><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">critical_section</span><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;"> crate</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> is commonly used to handle this functionality for a number of architectures, and can be extended to support more.</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">It can be useful to hook up functions for logging as well. Simple wrappers around the firmware’s existing logging functions can expose these to Rust and be used in place of </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">print</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> or </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">eprint </span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">and the like. A convenient option is to </span><a href="https://google.github.io/comprehensive-rust/bare-metal/aps/logging.html" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">implement the </span><span style="color: #0f9d58; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">Log</span><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;"> trait</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">.</span></p><h2 dir="ltr" style="line-height: 1.38; margin-bottom: 10pt; margin-top: 18pt;"><span style="font-family: Arial, sans-serif; font-size: 16pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; font-weight: 400; vertical-align: baseline; white-space-collapse: preserve;">Fallible Allocations and </span><span style="color: #0f9d58; font-family: "Roboto Mono", monospace; font-size: 16pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; font-weight: 400; vertical-align: baseline; white-space-collapse: preserve;">alloc</span></h2><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">Rusts </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">alloc</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> crate normally assumes that allocations are infallible (that is, memory allocations won’t fail). However due to memory constraints this isn’t true in most bare-metal environments. Under normal circumstances </span><a href="https://doc.rust-lang.org/stable/std/alloc/fn.handle_alloc_error.html" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">Rust panics and/or aborts</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> when an allocation fails; this may be acceptable behavior for some bare-metal environments, in which case there are no further considerations when using </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">alloc</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">.</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">If there’s a clear justification or requirement for fallible allocations however, additional effort is required to ensure that either allocations can’t fail or that failures are handled. </span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">One approach is to use a crate that provides statically allocated fallible collections, such as the </span><a href="https://docs.rs/heapless/latest/heapless/index.html" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">heapless</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> crate, or dynamic fallible allocations like </span><a href="https://docs.rs/fallible_vec/latest/fallible_vec/" style="text-decoration-line: none;"><span style="color: #0f9d58; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">fallible_vec</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">. Another is to exclusively use </span><span style="color: #0f9d58; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">try_*</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> methods such as </span><span style="color: #0f9d58; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">Vec::try_reserve</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">, which check if the allocation is possible.</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">Rust is in the process of formalizing better support for fallible allocations, with an </span><a href="https://doc.rust-lang.org/std/alloc/trait.Allocator.html" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">experimental allocator in nightly</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> allowing </span><a href="https://doc.rust-lang.org/std/alloc/struct.AllocError.html" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">failed allocations</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> to be handled by the implementation. There is also the unstable cfg flag for </span><span style="color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">alloc</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> called </span><a href="https://github.com/rust-lang/rust/pull/84266" style="text-decoration-line: none;"><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">no_global_oom_handling</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> which removes the infallible methods, ensuring they are not used.</span></p><h2 dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 18pt;"><span style="font-family: Arial, sans-serif; font-size: 16pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; font-weight: 400; vertical-align: baseline; white-space-collapse: preserve;">Build Optimizations</span></h2><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">Building the Rust library with LTO is necessary to optimize for code size. The existing C/C++ code base does not need to be built with LTO when passing </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">-C lto=true</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> to </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">rustc</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">. Additionally, setting </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">-C codegen-unit=1</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> results in further optimizations in addition to reproducibility. </span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">If using Cargo to build, the following Cargo.toml settings are recommended to reduce the output library size:</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #188038; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">[profile.release]</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #188038; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">panic</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #188038; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">=</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #188038; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">"abort"</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #188038; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">lto</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #188038; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">=</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #188038; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">true</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #188038; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">codegen-units</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #188038; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">=</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #188038; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">1</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #188038; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">strip = "symbols"</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #188038; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"># opt-level "z" may produce better results in some circumstances</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #188038; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">opt-level</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #188038; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">=</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #188038; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">"s" </span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">Passing the </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">-Z remap-cwd-prefix=.</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> flag to </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">rustc</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> or to Cargo via the </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">RUSTFLAGS</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> env var when building with Cargo to strip cwd path strings.</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">In terms of performance, Rust demonstrates similar performance to C. The most relevant example may be the Rust binder Linux kernel driver, which found “</span><a href="https://lore.kernel.org/rust-for-linux/20231101-rust-binder-v1-0-08ba9197f637@google.com/#:~:text=We%27ve%20found%20that%20Rust%20binder%20has%20similar%20performance%20to%20C%20binder%20on%20the%0AbinderThroughputTest%20benchmark.%20The%20average%20latencies%20fluctuate%20between%0A%2D1.96%25%20and%20%2B1.38%25." style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">that Rust binder has similar performance to C binder</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">”.</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">When linking LTO’d Rust staticlibs together with C/C++, it’s recommended to ensure a single Rust staticlib ends up in the final linkage, otherwise there may be </span><a href="https://github.com/rust-lang/rust/issues/44322" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">duplicate symbol errors</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> when linking. This may mean combining multiple Rust shims into a single static library by re-exporting them from a wrapper module.</span></p><h1 dir="ltr" style="line-height: 1.38; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial, sans-serif; font-size: 20pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; font-weight: 400; vertical-align: baseline; white-space-collapse: preserve;">Memory Safety for Firmware, Today</span></h1><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">Using the process outlined in this blog post, You can begin to introduce Rust into large legacy firmware code bases immediately. Replacing security critical components with off-the-shelf open-source memory-safe implementations and developing new features in a memory safe language will lead to fewer critical vulnerabilities while also providing an </span><a href="https://opensource.googleblog.com/2023/06/rust-fact-vs-fiction-5-insights-from-googles-rust-journey-2022.html" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">improved developer experience</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">.</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Roboto, sans-serif; font-size: 12pt; font-style: italic; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">Special thanks to our colleagues who have supported and contributed to these efforts: Roger Piqueras Jover, Stephan Chen, Gil Cukierman, Andrew Walbran, and Erik Gilling </span></p><div><span style="font-family: Roboto, sans-serif; font-size: 12pt; font-style: italic; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"><br /></span></div></span></div> <span itemprop='author' itemscope='itemscope' itemtype='http://schema.org/Person'> <meta content='https://plus.google.com/116899029375914044550' itemprop='url'/> </span> </script> <noscript> <p style="text-align: left;"><span class="byline-author">Posted by Ivan Lozano and Dominik Maier, Android Team</span> <p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">Android's use of safe-by-design principles drives our adoption of memory-safe languages like Rust, making exploitation of the OS increasingly difficult with every release. To provide a secure foundation, we’re extending hardening and the use of </span><a href="https://security.googleblog.com/2023/10/bare-metal-rust-in-android.html" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">memory-safe languages to low-level firmware</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> (including in </span><a href="https://cs.android.com/android/platform/superproject/main/+/main:trusty/user/app/keymint/lib.rs;drc=4176f2465d7dc81c398730cb579c0a4949a9a832" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">Trusty apps</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">).</span></p><br /><p dir="ltr" style="line-height: 1.3800000000000001; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">In this blog post, we'll show you how to gradually introduce </span><a href="https://security.googleblog.com/2021/04/rust-in-android-platform.html#:~:text=But%20what%20about%20all%20that%20existing%20C%2B%2B%3F" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">Rust into your existing firmware</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">, prioritizing new code and the most security-critical code. You'll see how easy it is to boost security with drop-in Rust replacements, and we'll even demonstrate how the Rust toolchain can handle specialized bare-metal targets.</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">Drop-in Rust replacements for C code are not a novel idea and have been used in other cases, such as </span><a href="https://mail.gnome.org/archives/desktop-devel-list/2017-January/msg00001.html" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">librsvg’s adoption of Rust</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> which involved </span><a href="https://web.archive.org/web/20170928062853/https://people.gnome.org/~federico/blog/docs/fmq-porting-c-to-rust.pdf" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">replacing C functions with Rust functions</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> in-place. We seek to demonstrate that this approach is viable for firmware, providing a path to memory-safety in an efficient and effective manner.</span></p><h1 dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 20pt;"><span style="font-family: Arial, sans-serif; font-size: 20pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; font-weight: 400; vertical-align: baseline; white-space-collapse: preserve;">Memory Safety for Firmware</span></h1><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">Firmware serves as the interface between hardware and higher-level software. Due to the lack of software security mechanisms that are standard in higher-level software, vulnerabilities in firmware code can be dangerously exploited by malicious actors. Modern phones contain many coprocessors responsible for handling various operations, and each of these run their own firmware. Often, firmware consists of large legacy code bases written in memory-unsafe languages such as C or C++. Memory unsafety is the leading cause of vulnerabilities in </span><a href="https://source.android.com/docs/security/test/memory-safety" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">Android</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">, </span><a href="https://www.chromium.org/Home/chromium-security/memory-safety/" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">Chrome</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">, and many other code bases.</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">Rust provides a memory-safe alternative to C and C++ with comparable performance and code size. Additionally it supports interoperability with C with no overhead. The Android team has discussed </span><a href="https://security.googleblog.com/2023/10/bare-metal-rust-in-android.html" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">Rust for bare-metal firmware previously</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">, and has </span><a href="https://google.github.io/comprehensive-rust/bare-metal.html" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">developed training specifically for this domain</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">.</span></p><h1 dir="ltr" style="line-height: 1.38; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial, sans-serif; font-size: 20pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; font-weight: 400; vertical-align: baseline; white-space-collapse: preserve;">Incremental Rust Adoption</span></h1><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">Our incremental approach focusing on replacing new and highest risk existing code (for example, code which processes external untrusted input) can provide maximum security benefits with the least amount of effort. Simply writing any new code in Rust reduces the number of new vulnerabilities and over time can lead to a reduction in </span><a href="https://security.googleblog.com/2021/04/rust-in-android-platform.html" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">the number of outstanding vulnerabilities</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">.</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">You can replace existing C functionality by writing a thin Rust shim that translates between an existing Rust API and the C API the codebase expects. The C API is replicated and exported by the shim for the existing codebase to link against. The shim serves as </span><a href="https://doc.rust-lang.org/nomicon/ffi.html#calling-rust-code-from-c" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">a wrapper</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> around the Rust library API, bridging the existing C API and the Rust API. This is a common approach when rewriting or replacing existing libraries with a Rust alternative.</span></p><h1 dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 20pt;"><span style="font-family: Arial, sans-serif; font-size: 20pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; font-weight: 400; vertical-align: baseline; white-space-collapse: preserve;">Challenges and Considerations</span></h1><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">There are several challenges you need to consider before introducing Rust to your firmware codebase. In the following section we address the general state of </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">no_std</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> Rust (that is, bare-metal Rust code), how to find the right off-the-shelf crate (a rust library), porting an std crate to </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">no_std</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">, using Bindgen to produce FFI bindings, how to approach allocators and panics, and how to set up your toolchain.</span></p><h2 dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 18pt;"><span style="font-family: Arial, sans-serif; font-size: 16pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; font-weight: 400; vertical-align: baseline; white-space-collapse: preserve;">The Rust Standard Library and Bare-Metal Environments</span></h2><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">Rust's standard library consists of three crates: </span><a href="https://doc.rust-lang.org/core/" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">core</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">, </span><a href="https://doc.rust-lang.org/alloc/" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">alloc</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">, and </span><a href="https://doc.rust-lang.org/std/" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">std</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">. The </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">core</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> crate is always available. The </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">alloc</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> crate requires an allocator for its functionality. The </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">std</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> crate assumes a full-blown operating system and is commonly not supported in bare-metal environments. A third-party crate indicates it doesn’t rely on </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">std</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> through the crate-level </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">#![no_std] </span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">attribute. This crate is said to be </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">no_std</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> compatible. The rest of the blog will focus on these.</span></p><h2 dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 18pt;"><span style="font-family: Arial, sans-serif; font-size: 16pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; font-weight: 400; vertical-align: baseline; white-space-collapse: preserve;">Choosing a Component to Replace</span></h2><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">When choosing a component to replace, focus on self-contained components with robust testing. Ideally, the components functionality can be provided by an open-source implementation readily available which supports bare-metal environments.</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">Parsers which handle standard and commonly used data formats or protocols (such as, XML or DNS) are good initial candidates. This ensures the initial effort focuses on the challenges of integrating Rust with the existing code base and build system rather than the particulars of a complex component and simplifies testing. This approach eases introducing more Rust later on.</span></p><h2 dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 18pt;"><span style="font-family: Arial, sans-serif; font-size: 16pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; font-weight: 400; vertical-align: baseline; white-space-collapse: preserve;">Choosing a Pre-Existing Crate (Rust Library)</span></h2><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">Picking the right open-source crate (Rust library) to replace the chosen component is crucial. Things to consider are:</span></p><ul style="margin-bottom: 0; margin-top: 0; padding-inline-start: 48px;"><li aria-level="1" dir="ltr" style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; list-style-type: disc; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">Is the crate well maintained, for example, are open issues being addressed and does it use recent crate versions?</span></p></li><li aria-level="1" dir="ltr" style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; list-style-type: disc; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">How widely used is the crate? This may be used as a quality signal, but also important to consider in the context of using crates later on which may depend on it.</span></p></li><li aria-level="1" dir="ltr" style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; list-style-type: disc; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">Does the crate have acceptable documentation?</span></p></li><li aria-level="1" dir="ltr" style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; list-style-type: disc; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">Does it have acceptable test coverage?</span></p></li></ul><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">Additionally, the crate should ideally be </span><span style="color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">no_std</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> compatible, meaning the standard library is either unused or can be disabled. While a wide range of </span><span style="color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">no_std</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> compatible crates exist, others do not yet support this mode of operation – in those cases, see the next section on converting a </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">std</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> library to </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">no_std</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">.</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 10pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">By convention, crates which optionally support </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">no_std</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> will provide an </span><span style="color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">std</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> feature to indicate whether the standard library should be used. Similarly, the </span><span style="color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">alloc</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> feature usually indicates using an allocator is optional.</span></p><br /><div align="left" dir="ltr" style="margin-left: -14.25pt;"><table style="border-collapse: collapse; border: none;"><colgroup><col width="67"></col><col width="790"></col></colgroup><tbody><tr style="height: 54.75pt;"><td style="background-color: #e1f5fe; overflow-wrap: break-word; overflow: hidden; padding: 14.4pt 14.4pt 14.4pt 14.4pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #01579b; font-family: Roboto, sans-serif; font-size: 12pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"><span style="border: none; display: inline-block; height: 40px; overflow: hidden; width: 40px;"><img height="40" src="https://lh7-rt.googleusercontent.com/docsz/AD_4nXfPgBmsZj6ZTOto6Frw_NToC18UKVimJ8SHuCerE7W01D83L3qeJ-Qop83lTf1pvDshgc4CW3pap9aXpzVpSQZtG9EVZDzIQKD5x3vZ4yiEGDxMODTUTNZtlGMVy3Sh-I1i4x-QY8RzBAaqOSap6rGuC9WYg4pdhUO5vY_-OqUCcPssnZAYmUKb-FnV5Ainemg?key=NlrS0k5AvJIpHEA9_mIwTQ" style="margin-left: 0px; margin-top: 0px;" width="40" /></span></span></p></td><td style="background-color: #e1f5fe; overflow-wrap: break-word; overflow: hidden; padding: 14.4pt 14.4pt 14.4pt 14.4pt; vertical-align: middle;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #01579b; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; font-weight: 700; vertical-align: baseline; white-space-collapse: preserve;">Note:</span><span style="background-color: transparent; color: #01579b; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> Even when a library declares </span><span style="background-color: transparent; color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">#![no_std] </span><span style="background-color: transparent; color: #01579b; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">in its source, there is no guarantee that its dependencies don’t depend on </span><span style="background-color: transparent; color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">std</span><span style="background-color: transparent; color: #01579b; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">. We recommend looking through the dependency tree to ensure that all dependencies support </span><span style="background-color: transparent; color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">no_std</span><span style="background-color: transparent; color: #01579b; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">, or test whether the library compiles for a </span><span style="background-color: transparent; color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">no_std</span><span style="background-color: transparent; color: #01579b; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> target. The only way to know is currently by trying to compile the crate for a bare-metal target.</span></p></td></tr></tbody></table></div><br /><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 10pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">For example, one approach is to run </span><span style="color: #0f9d58; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">cargo check</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> with a bare-metal toolchain provided through </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">rustup</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">:</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #188038; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">$ rustup target add aarch64-unknown-none</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #188038; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">$ cargo check</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #188038; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">--target</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #188038; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">aarch64-unknown-none --no-default-features</span></p><br /><h2 dir="ltr" style="line-height: 1.38; margin-bottom: 10pt; margin-top: 14pt;"><span style="font-family: "Google Sans", sans-serif; font-size: 16pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; font-weight: 400; vertical-align: baseline; white-space-collapse: preserve;">Porting a </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 16pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; font-weight: 400; vertical-align: baseline; white-space-collapse: preserve;">std</span><span style="font-family: "Google Sans", sans-serif; font-size: 16pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; font-weight: 400; vertical-align: baseline; white-space-collapse: preserve;"> Library to </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 16pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; font-weight: 400; vertical-align: baseline; white-space-collapse: preserve;">no_std</span></h2><p dir="ltr" style="line-height: 1.38; margin-bottom: 10pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">If a library does not support </span><span style="color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">no_std</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">, it might still be possible to port it to a bare-metal environment – especially file format parsers and other OS agnostic workloads. Higher-level functionality such as file handling, threading, and async code may present more of a challenge. In those cases, such functionality can be hidden behind feature flags to still provide the core functionality in a </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">no_std</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> build.</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 10pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">To port a </span><span style="color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">std</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> crate to </span><span style="color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">no_std</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> (</span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">core</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">+</span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">alloc</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">):</span></p><ul style="margin-bottom: 0; margin-top: 0; padding-inline-start: 48px;"><li aria-level="1" dir="ltr" style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; list-style-type: disc; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">In the </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">cargo.toml</span><span style="font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;"> file, add a </span><span style="color: #0d904f; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">std</span><span style="font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;"> feature, then add this </span><span style="color: #0d904f; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">std</span><span style="font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;"> feature to the </span><span style="color: #0d904f; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">default </span><span style="font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">features</span></p></li><li aria-level="1" dir="ltr" style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; list-style-type: disc; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="line-height: 1.38; margin-bottom: 10pt; margin-top: 0pt;"><span style="font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">Add the following lines to the top of the </span><span style="color: #0d904f; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">lib.rs</span><span style="font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">:</span></p></li></ul><div align="left" dir="ltr" style="margin-left: 0pt;"><table style="border-collapse: collapse; border: none;"><colgroup></colgroup><tbody><tr style="height: 0pt;"><td style="background-color: #fafafa; border-bottom: solid #e0e0e0 1pt; border-left: solid #e0e0e0 1pt; border-right: solid #e0e0e0 1pt; border-top: solid #e0e0e0 1pt; overflow-wrap: break-word; overflow: hidden; padding: 5pt 5pt 5pt 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #455a64; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">#![no_std]</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #455a64; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">#[cfg(feature = "std")]</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #9c27b0; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">extern</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> crate std</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">;</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #9c27b0; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">extern</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> crate alloc</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">;</span></p></td></tr></tbody></table></div><p dir="ltr" style="line-height: 1.38; margin-bottom: 10pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">Then, iteratively fix all occurring compiler errors as follows:</span></p><ol style="margin-bottom: 0; margin-top: 0; padding-inline-start: 48px;"><li aria-level="1" dir="ltr" style="font-family: "Google Sans", sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; list-style-type: lower-alpha; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">Move any </span><span style="color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">use</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;"> directives from </span><span style="color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">std</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;"> to either </span><span style="color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">core</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;"> or </span><span style="color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">alloc</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">.</span></p></li><li aria-level="1" dir="ltr" style="font-family: "Google Sans", sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; list-style-type: lower-alpha; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">Add </span><span style="color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">use</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;"> directives for all types that would otherwise automatically be imported by the </span><a href="https://doc.rust-lang.org/std/prelude/index.html" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; text-wrap: wrap; vertical-align: baseline;">std prelude</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">, such as </span><span style="color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">alloc::vec::Vec</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;"> and</span><span style="color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;"> alloc::string::String</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">.</span></p></li><li aria-level="1" dir="ltr" style="font-family: "Google Sans", sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; list-style-type: lower-alpha; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">Hide anything that doesn't exist in </span><span style="color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">core</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;"> or </span><span style="color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">alloc</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;"> and cannot otherwise be supported in the </span><span style="color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">no_std</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;"> build (such as file system accesses) behind a </span><span style="color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">#[cfg(feature = </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">"</span><span style="color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">std</span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">"</span><span style="color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">)] </span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">guard.</span></p></li><li aria-level="1" dir="ltr" style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; list-style-type: lower-alpha; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">Anything that needs to interact with the embedded environment may need to be explicitly handled, such as functions for I/O. These likely need to be behind a </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">#[cfg(not(feature = "std"))]</span><span style="font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;"> guard.</span></p></li><li aria-level="1" dir="ltr" style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; list-style-type: lower-alpha; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="line-height: 1.38; margin-bottom: 10pt; margin-top: 0pt;"><span style="font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">Disable </span><span style="color: #0d904f; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">std</span><span style="font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;"> for all dependencies (that is, change their definitions in </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">Cargo.toml</span><span style="font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-wrap: wrap; vertical-align: baseline;">, if using Cargo).</span></p></li></ol><p dir="ltr" style="line-height: 1.38; margin-bottom: 10pt; margin-top: 0pt;"><span style="font-family: "Google Sans", sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">This needs to be repeated for all dependencies within the crate dependency tree that do not support </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">no_std</span><span style="font-family: "Google Sans", sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> yet.</span></p><h1 dir="ltr" style="line-height: 1.38; margin-bottom: 10pt; margin-top: 20pt;"><span style="font-family: Arial, sans-serif; font-size: 20pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; font-weight: 400; vertical-align: baseline; white-space-collapse: preserve;">Custom Target Architectures</span></h1><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">There are a number of officially </span><a href="https://doc.rust-lang.org/rustc/platform-support.html" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">supported targets</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> by the Rust compiler, however, many bare-metal targets are missing from that list. Thankfully, the Rust compiler lowers to LLVM IR and uses an internal copy of LLVM to lower to machine code. Thus, it can support any target architecture that LLVM supports by defining a custom target.</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">Defining a custom target requires a toolchain built with the </span><a href="https://github.com/rust-lang/rust/blob/master/config.example.toml#L577-L580" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">channel set to dev or nightly</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">. Rust’s </span><a href="https://docs.rust-embedded.org/embedonomicon/custom-target.html" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">Embedonomicon</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> has a wealth of information on this subject and should be referred to as the source of truth. </span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">To give a quick overview, a custom target JSON file can be constructed by finding a similar supported target and dumping the JSON representation:</span></p><br /><div align="left" dir="ltr" style="margin-left: 0pt;"><table style="border-collapse: collapse; border: none;"><colgroup></colgroup><tbody><tr style="height: 0pt;"><td style="background-color: #fafafa; border-bottom: solid #e0e0e0 1pt; border-left: solid #e0e0e0 1pt; border-right: solid #e0e0e0 1pt; border-top: solid #e0e0e0 1pt; overflow-wrap: break-word; overflow: hidden; padding: 5pt 5pt 5pt 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">$ rustc </span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">--</span><span style="background-color: transparent; color: #9c27b0; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">print</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> target</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">-</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">list</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">[...]</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">armv7a</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">-</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">none</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">-</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">eabi</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">[...]</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">$ rustc </span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">-</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">Z unstable</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">-</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">options </span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">--</span><span style="background-color: transparent; color: #9c27b0; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">print</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> target</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">-</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">spec</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">-</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">json </span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">--</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">target armv7a</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">-</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">none</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">-</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">eabi</span></p></td></tr></tbody></table></div><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">This will print out a target JSON that looks something like:</span></p><div align="left" dir="ltr" style="margin-left: 0pt;"><table style="border-collapse: collapse; border: none;"><colgroup></colgroup><tbody><tr style="height: 0pt;"><td style="background-color: #fafafa; border-bottom: solid #e0e0e0 1pt; border-left: solid #e0e0e0 1pt; border-right: solid #e0e0e0 1pt; border-top: solid #e0e0e0 1pt; overflow-wrap: break-word; overflow: hidden; padding: 5pt 5pt 5pt 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">$ rustc </span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">--</span><span style="background-color: transparent; color: #9c27b0; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">print</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> target</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">-</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">spec</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">-</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">json </span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">-</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">Z unstable</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">-</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">options </span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">--</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">target</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">=</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">armv7a</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">-</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">none</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">-</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">eabi</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">{</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">  </span><span style="background-color: transparent; color: #0f9d58; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">"abi"</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">:</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="background-color: transparent; color: #0f9d58; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">"eabi"</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">,</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">  </span><span style="background-color: transparent; color: #0f9d58; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">"arch"</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">:</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="background-color: transparent; color: #0f9d58; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">"arm"</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">,</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">  </span><span style="background-color: transparent; color: #0f9d58; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">"c-enum-min-bits"</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">:</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="background-color: transparent; color: #c53929; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">8</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">,</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">  </span><span style="background-color: transparent; color: #0f9d58; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">"crt-objects-fallback"</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">:</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="background-color: transparent; color: #0f9d58; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">"false"</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">,</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">  </span><span style="background-color: transparent; color: #0f9d58; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">"data-layout"</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">:</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="background-color: transparent; color: #0f9d58; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">"e-m:e-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64"</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">,</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">  </span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">[...]</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">}</span></p></td></tr></tbody></table></div><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">This output can provide a starting point for defining your target. Of particular note, the data-layout field is defined in the </span><a href="https://llvm.org/docs/LangRef.html#data-layout" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">LLVM documentation</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">.</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">Once the target is defined, </span><span style="color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">libcore</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> and </span><span style="color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">liballoc</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> (and </span><span style="color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">libstd</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">, if applicable) must be built from source for the newly defined target. If using Cargo, building with </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">-Z build-std</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> accomplishes this, indicating that these libraries should be built from source for your target along with your crate module:</span></p><div align="left" dir="ltr" style="margin-left: 0pt;"><table style="border-collapse: collapse; border: none;"><colgroup></colgroup><tbody><tr style="height: 0pt;"><td style="background-color: #fafafa; border-bottom: solid #e0e0e0 1pt; border-left: solid #e0e0e0 1pt; border-right: solid #e0e0e0 1pt; border-top: solid #e0e0e0 1pt; overflow-wrap: break-word; overflow: hidden; padding: 5pt 5pt 5pt 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #455a64; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"># set build-std to the list of libraries needed</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">cargo build </span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">-</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">Z build</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">-</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">std</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">=</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">core</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">,</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">alloc </span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">--</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">target my_target</span><span style="background-color: transparent; color: #616161; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">.</span><span style="background-color: transparent; font-family: Consolas, sans-serif; font-size: 10pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">json</span></p></td></tr></tbody></table></div><h2 dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 18pt;"><span style="font-family: Arial, sans-serif; font-size: 16pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; font-weight: 400; vertical-align: baseline; white-space-collapse: preserve;">Building Rust With LLVM Prebuilts</span></h2><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">If the bare-metal architecture is not supported by the LLVM bundled internal to the Rust toolchain, a custom Rust toolchain can be produced with any LLVM prebuilts that support the target.</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">The instructions for building a Rust toolchain can be found in detail in the </span><a href="https://rustc-dev-guide.rust-lang.org/building/how-to-build-and-run.html" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">Rust Compiler Developer Guide</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">. In the </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">config.toml</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">, </span><a href="https://github.com/rust-lang/rust/blob/036b38ced36b0ed16579f95b4647ba7424f6b1bc/config.example.toml#L790-L793" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">llvm-config</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> must be set to the path of the LLVM prebuilts.</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">You can find the latest Rust Toolchain supported by a particular version of LLVM by checking the </span><a href="https://github.com/rust-lang/rust/blob/master/RELEASES.md" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">release notes</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> and looking for releases which bump up the minimum supported LLVM version. For example, Rust </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">1.76</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> bumped the </span><a href="https://github.com/rust-lang/rust/blob/master/RELEASES.md" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">minimum LLVM to 16</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> and </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">1.73</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> bumped the </span><a href="https://github.com/rust-lang/rust/blob/master/RELEASES.md" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">minimum LLVM to 15</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">. That means with LLVM15 prebuilts, the latest Rust toolchain that can be built is </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">1.75</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">.</span></p><h1 dir="ltr" style="line-height: 1.38; margin-bottom: 10pt; margin-top: 20pt;"><span style="font-family: Arial, sans-serif; font-size: 20pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; font-weight: 400; vertical-align: baseline; white-space-collapse: preserve;">Creating a Drop-In Rust Shim</span></h1><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">To create a drop-in replacement for the C/C++ function or API being replaced, the shim needs two things: it must provide the same API as the replaced library and it must know how to run in the firmware’s bare-metal environment.</span></p><h2 dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 18pt;"><span style="font-family: Arial, sans-serif; font-size: 16pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; font-weight: 400; vertical-align: baseline; white-space-collapse: preserve;">Exposing the Same API</span></h2><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">The first is achieved by defining a Rust FFI interface with the same function signatures.</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">We try to keep the amount of unsafe Rust as minimal as possible by putting the actual implementation in a safe function and exposing a thin wrapper type around.</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">For example, the FreeRTOS </span><a href="https://github.com/FreeRTOS/coreJSON?tab=readme-ov-file#reference-example" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">coreJSON example</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> includes a </span><a href="https://github.com/FreeRTOS/coreJSON/blob/9ebaeb55cce39a6f79da9cceaa0cbc664a462c8b/source/include/core_json.h#L101-L102" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">JSON_Validate</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> C function with the following signature:</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">JSONStatus_t</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">JSON_Validate(</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">const</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #9334e6; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">char</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">*</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">buf,</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">size_t</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">max</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">);</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">We can write a shim in Rust between it and the memory safe </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">serde_json</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> crate to expose the C function signature. We try to keep the unsafe code to a minimum and call through to a safe function early:</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">#[no_mangle]</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">pub</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">unsafe</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #1967d2; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">extern</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #188038; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">"C"</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">fn</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">JSON_Validate(buf:</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">*const</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">c_char,</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">len:</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">usize)</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">-></span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">JSONStatus_t</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">{</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">    </span><span style="color: #1967d2; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">if</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">buf.is_null()</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">{</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">        </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">JSONStatus::JSONNullParameter</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">as</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">_</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">    </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">}</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #1967d2; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">else</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #1967d2; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">if</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">len</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">==</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #c5221f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">0</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">{</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">        </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">JSONStatus::JSONBadParameter</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">as</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">_</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">    </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">}</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #1967d2; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">else</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">{</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">        </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">json_validate(slice_from_raw_parts(buf</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">as</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">_,</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">len).as_ref().unwrap())</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">as</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">_</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">    </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">}</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">}</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #b80672; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">// No more unsafe code in here.</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">fn</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">json_validate(buf:</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">&[u8])</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">-></span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">JSONStatus</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">{</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">    </span><span style="color: #1967d2; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">if</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">serde_json::from_slice::<Value>(buf).is_ok()</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">{</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">        </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">JSONStatus::JSONSuccess</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">    </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">}</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #1967d2; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">else</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">{</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">        </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">ILLEGAL_DOC</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">    </span><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">}</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #37474f; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">}</span></p><br /><br /><div align="left" dir="ltr" style="margin-left: -16.5pt;"><table style="border-collapse: collapse; border: none;"><colgroup><col width="70"></col><col width="905"></col></colgroup><tbody><tr style="height: 54.75pt;"><td style="background-color: #e1f5fe; overflow-wrap: break-word; overflow: hidden; padding: 14.4pt 14.4pt 14.4pt 14.4pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #01579b; font-family: Roboto, sans-serif; font-size: 12pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"><span style="border: none; display: inline-block; height: 24px; overflow: hidden; width: 24px;"><img height="24" src="https://lh7-rt.googleusercontent.com/docsz/AD_4nXfPgBmsZj6ZTOto6Frw_NToC18UKVimJ8SHuCerE7W01D83L3qeJ-Qop83lTf1pvDshgc4CW3pap9aXpzVpSQZtG9EVZDzIQKD5x3vZ4yiEGDxMODTUTNZtlGMVy3Sh-I1i4x-QY8RzBAaqOSap6rGuC9WYg4pdhUO5vY_-OqUCcPssnZAYmUKb-FnV5Ainemg?key=NlrS0k5AvJIpHEA9_mIwTQ" style="margin-left: 0px; margin-top: 0px;" width="24" /></span></span></p></td><td style="background-color: #e1f5fe; overflow-wrap: break-word; overflow: hidden; padding: 14.4pt 14.4pt 14.4pt 14.4pt; vertical-align: middle;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #01579b; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; font-weight: 700; vertical-align: baseline; white-space-collapse: preserve;">Note:</span><span style="background-color: transparent; color: #01579b; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> This is a very simple example. For a highly resource constrained target, you can avoid </span><span style="background-color: transparent; color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">alloc</span><span style="background-color: transparent; color: #01579b; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> and use </span><a href="https://docs.rs/serde-json-core/latest/serde_json_core" style="text-decoration-line: none;"><span style="background-color: transparent; color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">serde_json_core</span></a><span style="background-color: transparent; color: #01579b; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">, which has even lower overhead but requires pre-defining the JSON structure so it can be allocated on the stack.</span></p></td></tr></tbody></table></div><br /><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">For further details on how to create an FFI interface, </span><a href="https://doc.rust-lang.org/nomicon/ffi.html" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">the Rustinomicon covers this topic extensively</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">.</span></p><h2 dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 18pt;"><span style="font-family: Arial, sans-serif; font-size: 16pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; font-weight: 400; vertical-align: baseline; white-space-collapse: preserve;">Calling Back to C/C++ Code</span></h2><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">In order for any Rust component to be functional within a C-based firmware, it will need to call back into the C code for things such as allocations or logging. Thankfully, there are a variety of tools available which automatically generate Rust FFI bindings to C. That way, C functions can easily be invoked from Rust.</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">The standard means of doing this is with the </span><a href="https://github.com/rust-lang/rust-bindgen" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">Bindgen</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> tool. You can use Bindgen to parse all relevant C headers that define the functions Rust needs to call into. It's important to invoke Bindgen with the same </span><span style="color: #0f9d58; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">CFLAGS</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> as the code in question is built with, to ensure that the bindings are generated correctly.</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">Experimental support for producing </span><a href="https://github.com/rust-lang/rust-bindgen/discussions/2405" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">bindings to static inline functions</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> is also available.</span></p><h2 dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 18pt;"><span style="font-family: Arial, sans-serif; font-size: 16pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; font-weight: 400; vertical-align: baseline; white-space-collapse: preserve;">Hooking Up The Firmware’s Bare-Metal Environment</span></h2><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">Next we need to hook up Rust panic handlers, global allocators, and critical section handlers to the existing code base. This requires producing definitions for each of these which call into the existing firmware C functions.</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">The Rust panic handler must be defined to handle unexpected states or failed assertions. A custom panic handler can be defined via the </span><a href="https://doc.rust-lang.org/nomicon/panic-handler.html" style="text-decoration-line: none;"><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">panic_handler</span><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;"> attribute</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">. This is specific to the target and should, in most cases, either point to an abort function for the current task/process, or a panic function provided by the environment.</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">If an allocator is available in the firmware and the crate relies on the </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">alloc</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> crate, the Rust allocator can be hooked up by </span><a href="https://doc.rust-lang.org/stable/core/alloc/trait.GlobalAlloc.html" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">defining a global allocator implementing GlobalAlloc</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">.</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">If the crate in question relies on concurrency, critical sections will need to be handled. Rust's </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">core</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> or </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">alloc</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> crates do not directly provide a means for defining this, however the </span><a href="https://docs.rs/critical-section/latest/critical_section/" style="text-decoration-line: none;"><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">critical_section</span><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;"> crate</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> is commonly used to handle this functionality for a number of architectures, and can be extended to support more.</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">It can be useful to hook up functions for logging as well. Simple wrappers around the firmware’s existing logging functions can expose these to Rust and be used in place of </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">print</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> or </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">eprint </span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">and the like. A convenient option is to </span><a href="https://google.github.io/comprehensive-rust/bare-metal/aps/logging.html" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">implement the </span><span style="color: #0f9d58; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">Log</span><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;"> trait</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">.</span></p><h2 dir="ltr" style="line-height: 1.38; margin-bottom: 10pt; margin-top: 18pt;"><span style="font-family: Arial, sans-serif; font-size: 16pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; font-weight: 400; vertical-align: baseline; white-space-collapse: preserve;">Fallible Allocations and </span><span style="color: #0f9d58; font-family: "Roboto Mono", monospace; font-size: 16pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; font-weight: 400; vertical-align: baseline; white-space-collapse: preserve;">alloc</span></h2><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">Rusts </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">alloc</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> crate normally assumes that allocations are infallible (that is, memory allocations won’t fail). However due to memory constraints this isn’t true in most bare-metal environments. Under normal circumstances </span><a href="https://doc.rust-lang.org/stable/std/alloc/fn.handle_alloc_error.html" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">Rust panics and/or aborts</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> when an allocation fails; this may be acceptable behavior for some bare-metal environments, in which case there are no further considerations when using </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">alloc</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">.</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">If there’s a clear justification or requirement for fallible allocations however, additional effort is required to ensure that either allocations can’t fail or that failures are handled. </span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">One approach is to use a crate that provides statically allocated fallible collections, such as the </span><a href="https://docs.rs/heapless/latest/heapless/index.html" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">heapless</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> crate, or dynamic fallible allocations like </span><a href="https://docs.rs/fallible_vec/latest/fallible_vec/" style="text-decoration-line: none;"><span style="color: #0f9d58; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">fallible_vec</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">. Another is to exclusively use </span><span style="color: #0f9d58; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">try_*</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> methods such as </span><span style="color: #0f9d58; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">Vec::try_reserve</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">, which check if the allocation is possible.</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">Rust is in the process of formalizing better support for fallible allocations, with an </span><a href="https://doc.rust-lang.org/std/alloc/trait.Allocator.html" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">experimental allocator in nightly</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> allowing </span><a href="https://doc.rust-lang.org/std/alloc/struct.AllocError.html" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">failed allocations</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> to be handled by the implementation. There is also the unstable cfg flag for </span><span style="color: #0d904f; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">alloc</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> called </span><a href="https://github.com/rust-lang/rust/pull/84266" style="text-decoration-line: none;"><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">no_global_oom_handling</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> which removes the infallible methods, ensuring they are not used.</span></p><h2 dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 18pt;"><span style="font-family: Arial, sans-serif; font-size: 16pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; font-weight: 400; vertical-align: baseline; white-space-collapse: preserve;">Build Optimizations</span></h2><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">Building the Rust library with LTO is necessary to optimize for code size. The existing C/C++ code base does not need to be built with LTO when passing </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">-C lto=true</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> to </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">rustc</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">. Additionally, setting </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">-C codegen-unit=1</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> results in further optimizations in addition to reproducibility. </span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">If using Cargo to build, the following Cargo.toml settings are recommended to reduce the output library size:</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #188038; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">[profile.release]</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #188038; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">panic</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #188038; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">=</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #188038; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">"abort"</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #188038; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">lto</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #188038; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">=</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #188038; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">true</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #188038; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">codegen-units</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #188038; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">=</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #188038; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">1</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #188038; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">strip = "symbols"</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #188038; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"># opt-level "z" may produce better results in some circumstances</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #188038; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">opt-level</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #188038; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">=</span><span style="font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> </span><span style="color: #188038; font-family: "Roboto Mono", monospace; font-size: 9pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">"s" </span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">Passing the </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">-Z remap-cwd-prefix=.</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> flag to </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">rustc</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> or to Cargo via the </span><span style="color: #0d904f; font-family: Consolas, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">RUSTFLAGS</span><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> env var when building with Cargo to strip cwd path strings.</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">In terms of performance, Rust demonstrates similar performance to C. The most relevant example may be the Rust binder Linux kernel driver, which found “</span><a href="https://lore.kernel.org/rust-for-linux/20231101-rust-binder-v1-0-08ba9197f637@google.com/#:~:text=We%27ve%20found%20that%20Rust%20binder%20has%20similar%20performance%20to%20C%20binder%20on%20the%0AbinderThroughputTest%20benchmark.%20The%20average%20latencies%20fluctuate%20between%0A%2D1.96%25%20and%20%2B1.38%25." style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">that Rust binder has similar performance to C binder</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">”.</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">When linking LTO’d Rust staticlibs together with C/C++, it’s recommended to ensure a single Rust staticlib ends up in the final linkage, otherwise there may be </span><a href="https://github.com/rust-lang/rust/issues/44322" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">duplicate symbol errors</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"> when linking. This may mean combining multiple Rust shims into a single static library by re-exporting them from a wrapper module.</span></p><h1 dir="ltr" style="line-height: 1.38; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial, sans-serif; font-size: 20pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; font-weight: 400; vertical-align: baseline; white-space-collapse: preserve;">Memory Safety for Firmware, Today</span></h1><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">Using the process outlined in this blog post, You can begin to introduce Rust into large legacy firmware code bases immediately. Replacing security critical components with off-the-shelf open-source memory-safe implementations and developing new features in a memory safe language will lead to fewer critical vulnerabilities while also providing an </span><a href="https://opensource.googleblog.com/2023/06/rust-fact-vs-fiction-5-insights-from-googles-rust-journey-2022.html" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space-collapse: preserve;">improved developer experience</span></a><span style="font-family: Arial, sans-serif; font-size: 11pt; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">.</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Roboto, sans-serif; font-size: 12pt; font-style: italic; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;">Special thanks to our colleagues who have supported and contributed to these efforts: Roger Piqueras Jover, Stephan Chen, Gil Cukierman, Andrew Walbran, and Erik Gilling </span></p><div><span style="font-family: Roboto, sans-serif; font-size: 12pt; font-style: italic; font-variant-alternates: normal; font-variant-east-asian: normal; font-variant-numeric: normal; font-variant-position: normal; vertical-align: baseline; white-space-collapse: preserve;"><br /></span></div></span></div> <span itemprop='author' itemscope='itemscope' itemtype='http://schema.org/Person'> <meta 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class='post-count-link' href='https://security.googleblog.com/2020/'> 2020 </a> </div> <div class='items'> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2020/12/'> Dec </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2020/11/'> Nov </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2020/10/'> Oct </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2020/09/'> Sep </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2020/08/'> Aug </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2020/07/'> Jul </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2020/06/'> Jun </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2020/05/'> May </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2020/04/'> Apr </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2020/03/'> Mar </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2020/02/'> Feb </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2020/01/'> Jan </a> </div> <div class='items'> </div> </li> </ul> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class='intervalToggle'> <span class='new-toggle' href='javascript:void(0)'> <i class='material-icons arrow'>  </i> </span> <a class='toggle' href='javascript:void(0)' style='display: none'> <span class='zippy'> <i class='material-icons'>  </i>   </span> </a> <a class='post-count-link' href='https://security.googleblog.com/2019/'> 2019 </a> </div> <div class='items'> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2019/12/'> Dec </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2019/11/'> Nov </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2019/10/'> Oct </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2019/09/'> Sep </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2019/08/'> Aug </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2019/07/'> Jul </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2019/06/'> Jun </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2019/05/'> May </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2019/04/'> Apr </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2019/03/'> Mar </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2019/02/'> Feb </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2019/01/'> Jan </a> </div> <div class='items'> </div> </li> </ul> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class='intervalToggle'> <span class='new-toggle' href='javascript:void(0)'> <i class='material-icons arrow'>  </i> </span> <a class='toggle' href='javascript:void(0)' style='display: none'> <span class='zippy'> <i class='material-icons'>  </i>   </span> </a> <a class='post-count-link' href='https://security.googleblog.com/2018/'> 2018 </a> </div> <div class='items'> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2018/12/'> Dec </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2018/11/'> Nov </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2018/10/'> Oct </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2018/09/'> Sep </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2018/08/'> Aug </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2018/07/'> Jul </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2018/06/'> Jun </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2018/05/'> May </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2018/04/'> Apr </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2018/03/'> Mar </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2018/02/'> Feb </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2018/01/'> Jan </a> </div> <div class='items'> </div> </li> </ul> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class='intervalToggle'> <span class='new-toggle' href='javascript:void(0)'> <i class='material-icons arrow'>  </i> </span> <a class='toggle' href='javascript:void(0)' style='display: none'> <span class='zippy'> <i class='material-icons'>  </i>   </span> </a> <a class='post-count-link' href='https://security.googleblog.com/2017/'> 2017 </a> </div> <div class='items'> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2017/12/'> Dec </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2017/11/'> Nov </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2017/10/'> Oct </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2017/09/'> Sep </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2017/07/'> Jul </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2017/06/'> Jun </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2017/05/'> May </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2017/04/'> Apr </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2017/03/'> Mar </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2017/02/'> Feb </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2017/01/'> Jan </a> </div> <div class='items'> </div> </li> </ul> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class='intervalToggle'> <span class='new-toggle' href='javascript:void(0)'> <i class='material-icons arrow'>  </i> </span> <a class='toggle' href='javascript:void(0)' style='display: none'> <span class='zippy'> <i class='material-icons'>  </i>   </span> </a> <a class='post-count-link' href='https://security.googleblog.com/2016/'> 2016 </a> </div> <div class='items'> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2016/12/'> Dec </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2016/11/'> Nov </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2016/10/'> Oct </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2016/09/'> Sep </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2016/08/'> Aug </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2016/07/'> Jul </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2016/06/'> Jun </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2016/05/'> May </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2016/04/'> Apr </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2016/03/'> Mar </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2016/02/'> Feb </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2016/01/'> Jan </a> </div> <div class='items'> </div> </li> </ul> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class='intervalToggle'> <span class='new-toggle' href='javascript:void(0)'> <i class='material-icons arrow'>  </i> </span> <a class='toggle' href='javascript:void(0)' style='display: none'> <span class='zippy'> <i class='material-icons'>  </i>   </span> </a> <a class='post-count-link' href='https://security.googleblog.com/2015/'> 2015 </a> </div> <div class='items'> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2015/12/'> Dec </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2015/11/'> Nov </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2015/10/'> Oct </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2015/09/'> Sep </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2015/08/'> Aug </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2015/07/'> Jul </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2015/06/'> Jun </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2015/05/'> May </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2015/04/'> Apr </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2015/03/'> Mar </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2015/02/'> Feb </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2015/01/'> Jan </a> </div> <div class='items'> </div> </li> </ul> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class='intervalToggle'> <span class='new-toggle' href='javascript:void(0)'> <i class='material-icons arrow'>  </i> </span> <a class='toggle' href='javascript:void(0)' style='display: none'> <span class='zippy'> <i class='material-icons'>  </i>   </span> </a> <a class='post-count-link' href='https://security.googleblog.com/2014/'> 2014 </a> </div> <div class='items'> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2014/12/'> Dec </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2014/11/'> Nov </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2014/10/'> Oct </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2014/09/'> Sep </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2014/08/'> Aug </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2014/07/'> Jul </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2014/06/'> Jun </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2014/04/'> Apr </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2014/03/'> Mar </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2014/02/'> Feb </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2014/01/'> Jan </a> </div> <div class='items'> </div> </li> </ul> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class='intervalToggle'> <span class='new-toggle' href='javascript:void(0)'> <i class='material-icons arrow'>  </i> </span> <a class='toggle' href='javascript:void(0)' style='display: none'> <span class='zippy'> <i class='material-icons'>  </i>   </span> </a> <a class='post-count-link' href='https://security.googleblog.com/2013/'> 2013 </a> </div> <div class='items'> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2013/12/'> Dec </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2013/11/'> Nov </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2013/10/'> Oct </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2013/08/'> Aug </a> </div> <div class='items'> 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<div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2013/01/'> Jan </a> </div> <div class='items'> </div> </li> </ul> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class='intervalToggle'> <span class='new-toggle' href='javascript:void(0)'> <i class='material-icons arrow'>  </i> </span> <a class='toggle' href='javascript:void(0)' style='display: none'> <span class='zippy'> <i class='material-icons'>  </i>   </span> </a> <a class='post-count-link' href='https://security.googleblog.com/2012/'> 2012 </a> </div> <div class='items'> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2012/12/'> Dec </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' 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class='post-count-link' href='https://security.googleblog.com/2012/03/'> Mar </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2012/02/'> Feb </a> </div> <div class='items'> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class=''> <a class='post-count-link' href='https://security.googleblog.com/2012/01/'> Jan </a> </div> <div class='items'> </div> </li> </ul> </div> </li> </ul> <ul class='hierarchy'> <li class='archivedate collapsed'> <div class='intervalToggle'> <span class='new-toggle' href='javascript:void(0)'> <i class='material-icons arrow'>  </i> </span> <a class='toggle' href='javascript:void(0)' style='display: none'> <span class='zippy'> <i class='material-icons'>  </i>   </span> </a> <a class='post-count-link' href='https://security.googleblog.com/2011/'> 2011 </a> </div> <div class='items'> <ul 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