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291 lines
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291 lines
12 KiB
HTML
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3 or
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any later version published by the Free Software Foundation; with the
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Texts being (a) (see below), and with the Back-Cover Texts being (b)
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(see below). A copy of the license is included in the section entitled
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"GNU Free Documentation License".
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(a) The FSF's Front-Cover Text is:
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A GNU Manual
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<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>Plugin API (GNU Compiler Collection (GCC) Internals)</title>
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<meta name="description" content="Plugin API (GNU Compiler Collection (GCC) Internals)">
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<meta name="keywords" content="Plugin API (GNU Compiler Collection (GCC) Internals)">
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<link href="index.html#Top" rel="start" title="Top">
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<link href="Option-Index.html#Option-Index" rel="index" title="Option Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Plugins.html#Plugins" rel="up" title="Plugins">
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<link href="Plugins-pass.html#Plugins-pass" rel="next" title="Plugins pass">
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<link href="Plugins-loading.html#Plugins-loading" rel="prev" title="Plugins loading">
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</style>
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</head>
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<body lang="en">
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<a name="Plugin-API"></a>
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<div class="header">
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<p>
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Next: <a href="Plugins-pass.html#Plugins-pass" accesskey="n" rel="next">Plugins pass</a>, Previous: <a href="Plugins-loading.html#Plugins-loading" accesskey="p" rel="prev">Plugins loading</a>, Up: <a href="Plugins.html#Plugins" accesskey="u" rel="up">Plugins</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="Plugin-API-1"></a>
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<h3 class="section">24.2 Plugin API</h3>
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<p>Plugins are activated by the compiler at specific events as defined in
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<samp>gcc-plugin.h</samp>. For each event of interest, the plugin should
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call <code>register_callback</code> specifying the name of the event and
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address of the callback function that will handle that event.
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</p>
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<p>The header <samp>gcc-plugin.h</samp> must be the first gcc header to be included.
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</p>
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<a name="Plugin-license-check"></a>
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<h4 class="subsection">24.2.1 Plugin license check</h4>
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<p>Every plugin should define the global symbol <code>plugin_is_GPL_compatible</code>
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to assert that it has been licensed under a GPL-compatible license.
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If this symbol does not exist, the compiler will emit a fatal error
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and exit with the error message:
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</p>
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<div class="smallexample">
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<pre class="smallexample">fatal error: plugin <var>name</var> is not licensed under a GPL-compatible license
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<var>name</var>: undefined symbol: plugin_is_GPL_compatible
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compilation terminated
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</pre></div>
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<p>The declared type of the symbol should be int, to match a forward declaration
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in <samp>gcc-plugin.h</samp> that suppresses C++ mangling. It does not need to be in
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any allocated section, though. The compiler merely asserts that
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the symbol exists in the global scope. Something like this is enough:
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</p>
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<div class="smallexample">
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<pre class="smallexample">int plugin_is_GPL_compatible;
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</pre></div>
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<a name="Plugin-initialization"></a>
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<h4 class="subsection">24.2.2 Plugin initialization</h4>
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<p>Every plugin should export a function called <code>plugin_init</code> that
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is called right after the plugin is loaded. This function is
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responsible for registering all the callbacks required by the plugin
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and do any other required initialization.
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</p>
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<p>This function is called from <code>compile_file</code> right before invoking
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the parser. The arguments to <code>plugin_init</code> are:
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</p>
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<ul>
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<li> <code>plugin_info</code>: Plugin invocation information.
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</li><li> <code>version</code>: GCC version.
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</li></ul>
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<p>The <code>plugin_info</code> struct is defined as follows:
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</p>
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<div class="smallexample">
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<pre class="smallexample">struct plugin_name_args
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{
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char *base_name; /* Short name of the plugin
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(filename without .so suffix). */
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const char *full_name; /* Path to the plugin as specified with
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-fplugin=. */
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int argc; /* Number of arguments specified with
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-fplugin-arg-.... */
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struct plugin_argument *argv; /* Array of ARGC key-value pairs. */
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const char *version; /* Version string provided by plugin. */
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const char *help; /* Help string provided by plugin. */
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}
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</pre></div>
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<p>If initialization fails, <code>plugin_init</code> must return a non-zero
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value. Otherwise, it should return 0.
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</p>
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<p>The version of the GCC compiler loading the plugin is described by the
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following structure:
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</p>
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<div class="smallexample">
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<pre class="smallexample">struct plugin_gcc_version
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{
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const char *basever;
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const char *datestamp;
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const char *devphase;
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const char *revision;
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const char *configuration_arguments;
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};
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</pre></div>
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<p>The function <code>plugin_default_version_check</code> takes two pointers to
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such structure and compare them field by field. It can be used by the
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plugin’s <code>plugin_init</code> function.
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</p>
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<p>The version of GCC used to compile the plugin can be found in the symbol
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<code>gcc_version</code> defined in the header <samp>plugin-version.h</samp>. The
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recommended version check to perform looks like
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</p>
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<div class="smallexample">
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<pre class="smallexample">#include "plugin-version.h"
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...
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int
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plugin_init (struct plugin_name_args *plugin_info,
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struct plugin_gcc_version *version)
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{
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if (!plugin_default_version_check (version, &gcc_version))
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return 1;
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}
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</pre></div>
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<p>but you can also check the individual fields if you want a less strict check.
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</p>
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<a name="Plugin-callbacks"></a>
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<h4 class="subsection">24.2.3 Plugin callbacks</h4>
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<p>Callback functions have the following prototype:
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</p>
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<div class="smallexample">
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<pre class="smallexample">/* The prototype for a plugin callback function.
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gcc_data - event-specific data provided by GCC
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user_data - plugin-specific data provided by the plug-in. */
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typedef void (*plugin_callback_func)(void *gcc_data, void *user_data);
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</pre></div>
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<p>Callbacks can be invoked at the following pre-determined events:
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</p>
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<div class="smallexample">
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<pre class="smallexample">enum plugin_event
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{
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PLUGIN_START_PARSE_FUNCTION, /* Called before parsing the body of a function. */
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PLUGIN_FINISH_PARSE_FUNCTION, /* After finishing parsing a function. */
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PLUGIN_PASS_MANAGER_SETUP, /* To hook into pass manager. */
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PLUGIN_FINISH_TYPE, /* After finishing parsing a type. */
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PLUGIN_FINISH_DECL, /* After finishing parsing a declaration. */
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PLUGIN_FINISH_UNIT, /* Useful for summary processing. */
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PLUGIN_PRE_GENERICIZE, /* Allows to see low level AST in C and C++ frontends. */
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PLUGIN_FINISH, /* Called before GCC exits. */
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PLUGIN_INFO, /* Information about the plugin. */
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PLUGIN_GGC_START, /* Called at start of GCC Garbage Collection. */
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PLUGIN_GGC_MARKING, /* Extend the GGC marking. */
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PLUGIN_GGC_END, /* Called at end of GGC. */
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PLUGIN_REGISTER_GGC_ROOTS, /* Register an extra GGC root table. */
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PLUGIN_ATTRIBUTES, /* Called during attribute registration */
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PLUGIN_START_UNIT, /* Called before processing a translation unit. */
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PLUGIN_PRAGMAS, /* Called during pragma registration. */
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/* Called before first pass from all_passes. */
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PLUGIN_ALL_PASSES_START,
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/* Called after last pass from all_passes. */
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PLUGIN_ALL_PASSES_END,
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/* Called before first ipa pass. */
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PLUGIN_ALL_IPA_PASSES_START,
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/* Called after last ipa pass. */
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PLUGIN_ALL_IPA_PASSES_END,
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/* Allows to override pass gate decision for current_pass. */
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PLUGIN_OVERRIDE_GATE,
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/* Called before executing a pass. */
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PLUGIN_PASS_EXECUTION,
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/* Called before executing subpasses of a GIMPLE_PASS in
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execute_ipa_pass_list. */
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PLUGIN_EARLY_GIMPLE_PASSES_START,
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/* Called after executing subpasses of a GIMPLE_PASS in
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execute_ipa_pass_list. */
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PLUGIN_EARLY_GIMPLE_PASSES_END,
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/* Called when a pass is first instantiated. */
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PLUGIN_NEW_PASS,
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/* Called when a file is #include-d or given via the #line directive.
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This could happen many times. The event data is the included file path,
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as a const char* pointer. */
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PLUGIN_INCLUDE_FILE,
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PLUGIN_EVENT_FIRST_DYNAMIC /* Dummy event used for indexing callback
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array. */
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};
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</pre></div>
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<p>In addition, plugins can also look up the enumerator of a named event,
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and / or generate new events dynamically, by calling the function
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<code>get_named_event_id</code>.
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</p>
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<p>To register a callback, the plugin calls <code>register_callback</code> with
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the arguments:
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</p>
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<ul>
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<li> <code>char *name</code>: Plugin name.
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</li><li> <code>int event</code>: The event code.
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</li><li> <code>plugin_callback_func callback</code>: The function that handles <code>event</code>.
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</li><li> <code>void *user_data</code>: Pointer to plugin-specific data.
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</li></ul>
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<p>For the <i>PLUGIN_PASS_MANAGER_SETUP</i>, <i>PLUGIN_INFO</i>, and
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<i>PLUGIN_REGISTER_GGC_ROOTS</i> pseudo-events the <code>callback</code> should be null,
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and the <code>user_data</code> is specific.
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</p>
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<p>When the <i>PLUGIN_PRAGMAS</i> event is triggered (with a null pointer as
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data from GCC), plugins may register their own pragmas. Notice that
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pragmas are not available from <samp>lto1</samp>, so plugins used with
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<code>-flto</code> option to GCC during link-time optimization cannot use
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pragmas and do not even see functions like <code>c_register_pragma</code> or
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<code>pragma_lex</code>.
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</p>
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<p>The <i>PLUGIN_INCLUDE_FILE</i> event, with a <code>const char*</code> file path as
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GCC data, is triggered for processing of <code>#include</code> or
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<code>#line</code> directives.
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</p>
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<p>The <i>PLUGIN_FINISH</i> event is the last time that plugins can call GCC
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functions, notably emit diagnostics with <code>warning</code>, <code>error</code>
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etc.
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</p>
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<hr>
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<div class="header">
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<p>
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Next: <a href="Plugins-pass.html#Plugins-pass" accesskey="n" rel="next">Plugins pass</a>, Previous: <a href="Plugins-loading.html#Plugins-loading" accesskey="p" rel="prev">Plugins loading</a>, Up: <a href="Plugins.html#Plugins" accesskey="u" rel="up">Plugins</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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