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malloc_usable_size
<html> <head> <title>malloc_usable_size</title> <META NAME="KEYWORDS" CONTENT="malloc_usable_size"> </head> <body BGCOLOR="#ffffff" LINK="#0000ff" VLINK="#0000ff" ALINK="#0000ff" TEXT="#000000"> <center> <h1><b>malloc_usable_size</b></h1></center> <PRE> <STRONG><A HREF="/man3/MALLOC_USABLE_SIZE">MALLOC_USABLE_SIZE(3)</A></STRONG> Linux Programmer's Manual <STRONG><A HREF="/man3/MALLOC_USABLE_SIZE">MALLOC_USABLE_SIZE(3)</A></STRONG> NAME malloc_usable_size - obtain size of block of memory allocated from heap SYNOPSIS #include <malloc.h> size_t malloc_usable_size (void *ptr); DESCRIPTION The malloc_usable_size() function returns the number of usable bytes in the block pointed to by ptr, a pointer to a block of memory allocated by <STRONG><A HREF="/man3/malloc">malloc(3)</A></STRONG> or a related function. RETURN VALUE malloc_usable_size() returns the number of usable bytes in the block of allocated memory pointed to by ptr. If ptr is NULL, 0 is returned. ATTRIBUTES For an explanation of the terms used in this section, see at- <STRONG><A HREF="/man7/tributes">tributes(7)</A></STRONG>. +---------------------+---------------+---------+ |Interface | Attribute | Value | +---------------------+---------------+---------+ |malloc_usable_size() | Thread safety | MT-Safe | +---------------------+---------------+---------+ CONFORMING TO This function is a GNU extension. NOTES The value returned by malloc_usable_size() may be greater than the re- quested size of the allocation because of alignment and minimum size constraints. Although the excess bytes can be overwritten by the ap- plication without ill effects, this is not good programming practice: the number of excess bytes in an allocation depends on the underlying implementation. The main use of this function is for debugging and introspection. SEE ALSO <STRONG><A HREF="/man3/malloc">malloc(3)</A></STRONG> COLOPHON This page is part of release 5.05 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at https://www.kernel.org/doc/man-pages/. GNU 2017-09-15 <STRONG><A HREF="/man3/MALLOC_USABLE_SIZE">MALLOC_USABLE_SIZE(3)</A></STRONG></PRE> <center> <h6>Man Pages Copyright Respective Owners. Site Copyright (C) 1994 - 2025 <a href="http://www.he.net">Hurricane Electric</a>. All Rights Reserved.</h6></center> </body> </html>