XSLoader - Dynamically load C libraries into Perl code

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Its primary purpose is to implement cheap automatic dynamic loading of Perl modules.</p> <p>For a more complicated interface, see <a href="/5.8.8/DynaLoader">DynaLoader</a>. Many (most) features of <code>DynaLoader</code> are not implemented in <code>XSLoader</code>, like for example the <code>dl_load_flags</code>, not honored by <code>XSLoader</code>.</p> <h2 id="Migration-from-DynaLoader"><a class="permalink" href="#Migration-from-DynaLoader">#</a><a id="Migration"></a>Migration from <code>DynaLoader</code></h2> <p>A typical module using <a href="/5.8.8/DynaLoader">DynaLoader</a> starts like this:</p> <pre><code>package YourPackage; require DynaLoader; our @ISA = qw( OnePackage OtherPackage DynaLoader ); our $VERSION = '0.01'; bootstrap YourPackage $VERSION;</code></pre> <p>Change this to</p> <pre><code>package YourPackage; use XSLoader; our @ISA = qw( OnePackage OtherPackage ); our $VERSION = '0.01'; XSLoader::load 'YourPackage', $VERSION;</code></pre> <p>In other words: replace <code>require DynaLoader</code> by <code>use XSLoader</code>, remove <code>DynaLoader</code> from <code>@ISA</code>, change <code>bootstrap</code> by <code>XSLoader::load</code>. Do not forget to quote the name of your package on the <code>XSLoader::load</code> line, and add comma (<code>,</code>) before the arguments (<code>$VERSION</code> above).</p> <p>Of course, if <code>@ISA</code> contained only <code>DynaLoader</code>, there is no need to have the <code>@ISA</code> assignment at all; moreover, if instead of <code>our</code> one uses the more backward-compatible</p> <pre><code>use vars qw($VERSION @ISA);</code></pre> <p>one can remove this reference to <code>@ISA</code> together with the <code>@ISA</code> assignment.</p> <p>If no <code>$VERSION</code> was specified on the <code>bootstrap</code> line, the last line becomes</p> <pre><code>XSLoader::load 'YourPackage';</code></pre> <h2 id="Backward-compatible-boilerplate"><a class="permalink" href="#Backward-compatible-boilerplate">#</a><a id="Backward"></a>Backward compatible boilerplate</h2> <p>If you want to have your cake and eat it too, you need a more complicated boilerplate.</p> <pre><code>package YourPackage; use vars qw($VERSION @ISA); @ISA = qw( OnePackage OtherPackage ); $VERSION = '0.01'; eval { require XSLoader; XSLoader::load('YourPackage', $VERSION); 1; } or do { require DynaLoader; push @ISA, 'DynaLoader'; bootstrap YourPackage $VERSION; };</code></pre> <p>The parentheses about <code>XSLoader::load()</code> arguments are needed since we replaced <code>use XSLoader</code> by <code>require</code>, so the compiler does not know that a function <code>XSLoader::load()</code> is present.</p> <p>This boilerplate uses the low-overhead <code>XSLoader</code> if present; if used with an antic Perl which has no <code>XSLoader</code>, it falls back to using <code>DynaLoader</code>.</p> <h1 id="Order-of-initialization:-early-load()"><a class="permalink" href="#Order-of-initialization:-early-load()">#</a><a id="Order"></a><a id="Order-of-initialization:-early-load"></a>Order of initialization: early load()</h1> <p><i>Skip this section if the XSUB functions are supposed to be called from other modules only; read it only if you call your XSUBs from the code in your module, or have a <code>BOOT:</code> section in your XS file (see <a href="/5.8.8/perlxs#The-BOOT%3A-Keyword">"The BOOT: Keyword" in perlxs</a>). What is described here is equally applicable to the <a href="/5.8.8/DynaLoader">DynaLoader</a> interface.</i></p> <p>A sufficiently complicated module using XS would have both Perl code (defined in <i>YourPackage.pm</i>) and XS code (defined in <i>YourPackage.xs</i>). If this Perl code makes calls into this XS code, and/or this XS code makes calls to the Perl code, one should be careful with the order of initialization.</p> <p>The call to <code>XSLoader::load()</code> (or <code>bootstrap()</code>) has three side effects:</p> <ul> <li><p>if <code>$VERSION</code> was specified, a sanity check is done to ensure that the versions of the <i>.pm</i> and the (compiled) <i>.xs</i> parts are compatible;</p> </li> <li><p>the XSUBs are made accessible from Perl;</p> </li> <li><p>if a <code>BOOT:</code> section was present in the <i>.xs</i> file, the code there is called.</p> </li> </ul> <p>Consequently, if the code in the <i>.pm</i> file makes calls to these XSUBs, it is convenient to have XSUBs installed before the Perl code is defined; for example, this makes prototypes for XSUBs visible to this Perl code. Alternatively, if the <code>BOOT:</code> section makes calls to Perl functions (or uses Perl variables) defined in the <i>.pm</i> file, they must be defined prior to the call to <code>XSLoader::load()</code> (or <code>bootstrap()</code>).</p> <p>The first situation being much more frequent, it makes sense to rewrite the boilerplate as</p> <pre><code>package YourPackage; use XSLoader; use vars qw($VERSION @ISA); BEGIN { @ISA = qw( OnePackage OtherPackage ); $VERSION = '0.01'; # Put Perl code used in the BOOT: section here XSLoader::load 'YourPackage', $VERSION; } # Put Perl code making calls into XSUBs here</code></pre> <h2 id="The-most-hairy-case"><a class="permalink" href="#The-most-hairy-case">#</a><a id="The"></a>The most hairy case</h2> <p>If the interdependence of your <code>BOOT:</code> section and Perl code is more complicated than this (e.g., the <code>BOOT:</code> section makes calls to Perl functions which make calls to XSUBs with prototypes), get rid of the <code>BOOT:</code> section altogether. Replace it with a function <code>onBOOT()</code>, and call it like this:</p> <pre><code>package YourPackage; use XSLoader; use vars qw($VERSION @ISA); BEGIN { @ISA = qw( OnePackage OtherPackage ); $VERSION = '0.01'; XSLoader::load 'YourPackage', $VERSION; } # Put Perl code used in onBOOT() function here; calls to XSUBs are # prototype-checked. onBOOT; # Put Perl initialization code assuming that XS is initialized here</code></pre> <h1 id="DIAGNOSTICS"><a class="permalink" href="#DIAGNOSTICS">#</a>DIAGNOSTICS</h1> <dl> <dt id="Can't-find-'%s'-symbol-in-%s"><a class="permalink" href="#Can't-find-'%25s'-symbol-in-%25s">#</a><a id="Can"></a><a id="Cant-find-s-symbol-in-s"></a>Can't find '%s' symbol in %s</dt> <dd> <p><b>(F)</b> The bootstrap symbol could not be found in the extension module.</p> </dd> <dt id="Can't-load-'%s'-for-module-%s:-%s"><a class="permalink" href="#Can't-load-'%25s'-for-module-%25s:-%25s">#</a><a id="Can1"></a><a id="Cant-load-s-for-module-s:-s"></a>Can't load '%s' for module %s: %s</dt> <dd> <p><b>(F)</b> The loading or initialisation of the extension module failed. The detailed error follows.</p> </dd> <dt id="Undefined-symbols-present-after-loading-%s:-%s"><a class="permalink" href="#Undefined-symbols-present-after-loading-%25s:-%25s">#</a><a id="Undefined"></a><a id="Undefined-symbols-present-after-loading-s:-s"></a>Undefined symbols present after loading %s: %s</dt> <dd> <p><b>(W)</b> As the message says, some symbols stay undefined although the extension module was correctly loaded and initialised. The list of undefined symbols follows.</p> </dd> <dt id="XSLoader::load('Your::Module',-$Your::Module::VERSION)"><a class="permalink" href="#XSLoader::load('Your::Module',-$Your::Module::VERSION)">#</a><a id="XSLoader"></a><a id="XSLoader::load-Your::Module-Your::Module::VERSION"></a>XSLoader::load('Your::Module', $Your::Module::VERSION)</dt> <dd> <p><b>(F)</b> You tried to invoke <code>load()</code> without any argument. You must supply a module name, and optionally its version.</p> </dd> </dl> <h1 id="LIMITATIONS"><a class="permalink" href="#LIMITATIONS">#</a>LIMITATIONS</h1> <p>To reduce the overhead as much as possible, only one possible location is checked to find the extension DLL (this location is where <code>make install</code> would put the DLL). If not found, the search for the DLL is transparently delegated to <code>DynaLoader</code>, which looks for the DLL along the <code>@INC</code> list.</p> <p>In particular, this is applicable to the structure of <code>@INC</code> used for testing not-yet-installed extensions. This means that running uninstalled extensions may have much more overhead than running the same extensions after <code>make install</code>.</p> <h1 id="BUGS"><a class="permalink" href="#BUGS">#</a>BUGS</h1> <p>Please report any bugs or feature requests via the perlbug(1) utility.</p> <h1 id="SEE-ALSO"><a class="permalink" href="#SEE-ALSO">#</a><a id="SEE"></a>SEE ALSO</h1> <p><a href="/5.8.8/DynaLoader">DynaLoader</a></p> <h1 id="AUTHORS"><a class="permalink" href="#AUTHORS">#</a>AUTHORS</h1> <p>Ilya Zakharevich originally extracted <code>XSLoader</code> from <code>DynaLoader</code>.</p> <p>CPAN version is currently maintained by S茅bastien Aperghis-Tramoni <sebastien@aperghis.net></p> <p>Previous maintainer was Michael G Schwern <schwern@pobox.com></p> <h1 id="COPYRIGHT"><a class="permalink" href="#COPYRIGHT">#</a>COPYRIGHT</h1> <p>This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.</p> </div> <div id="footer"> <p>Perldoc Browser is maintained by Dan Book (<a href="https://metacpan.org/author/DBOOK">DBOOK</a>). Please contact him via the <a href="https://github.com/Grinnz/perldoc-browser/issues">GitHub issue tracker</a> or <a href="mailto:dbook@cpan.org">email</a> regarding any issues with the site itself, search, or rendering of documentation.</p> <p>The Perl documentation is maintained by the Perl 5 Porters in the development of Perl. Please contact them via the <a href="https://github.com/Perl/perl5/issues">Perl issue tracker</a>, the <a href="https://lists.perl.org/list/perl5-porters.html">mailing list</a>, or <a href="https://kiwiirc.com/client/irc.perl.org/p5p">IRC</a> to report any issues with the contents or format of the documentation.</p> </div> </div> <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.5.1/jquery.slim.min.js" integrity="sha512-/DXTXr6nQodMUiq+IUJYCt2PPOUjrHJ9wFrqpJ3XkgPNOZVfMok7cRw6CSxyCQxXn6ozlESsSh1/sMCTF1rL/g==" crossorigin="anonymous"></script> <script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.16.1/umd/popper.min.js" integrity="sha512-ubuT8Z88WxezgSqf3RLuNi5lmjstiJcyezx34yIU2gAHonIi27Na7atqzUZCOoY4CExaoFumzOsFQ2Ch+I/HCw==" crossorigin="anonymous"></script> <script src="https://stackpath.bootstrapcdn.com/bootstrap/4.5.2/js/bootstrap.min.js" integrity="sha384-B4gt1jrGC7Jh4AgTPSdUtOBvfO8shuf57BaghqFfPlYxofvL8/KUEfYiJOMMV+rV" crossorigin="anonymous"></script> <script src="/js/highlight.pack.js"></script> <script>hljs.highlightAll();</script> </body> </html>

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XSLoader - Dynamically load C libraries into Perl code - Perldoc Browser