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<title>Plugins attr (GNU Compiler Collection (GCC) Internals)</title>
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<a name="Plugins-attr"></a>
<div class="header">
<p>
Next: <a href="Plugins-recording.html#Plugins-recording" accesskey="n" rel="next">Plugins recording</a>, Previous: <a href="Plugins-description.html#Plugins-description" accesskey="p" rel="prev">Plugins description</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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<hr>
<a name="Registering-custom-attributes-or-pragmas"></a>
<h3 class="section">24.6 Registering custom attributes or pragmas</h3>
<p>For analysis (or other) purposes it is useful to be able to add custom
attributes or pragmas.
</p>
<p>The <code>PLUGIN_ATTRIBUTES</code> callback is called during attribute
registration. Use the <code>register_attribute</code> function to register
custom attributes.
</p>
<div class="smallexample">
<pre class="smallexample">/* Attribute handler callback */
static tree
handle_user_attribute (tree *node, tree name, tree args,
int flags, bool *no_add_attrs)
{
return NULL_TREE;
}
/* Attribute definition */
static struct attribute_spec user_attr =
{ "user", 1, 1, false, false, false, false, handle_user_attribute, NULL };
/* Plugin callback called during attribute registration.
Registered with register_callback (plugin_name, PLUGIN_ATTRIBUTES, register_attributes, NULL)
*/
static void
register_attributes (void *event_data, void *data)
{
warning (0, G_("Callback to register attributes"));
register_attribute (&user_attr);
}
</pre></div>
<p>The <i>PLUGIN_PRAGMAS</i> callback is called once during pragmas
registration. Use the <code>c_register_pragma</code>,
<code>c_register_pragma_with_data</code>,
<code>c_register_pragma_with_expansion</code>,
<code>c_register_pragma_with_expansion_and_data</code> functions to register
custom pragmas and their handlers (which often want to call
<code>pragma_lex</code>) from <samp>c-family/c-pragma.h</samp>.
</p>
<div class="smallexample">
<pre class="smallexample">/* Plugin callback called during pragmas registration. Registered with
register_callback (plugin_name, PLUGIN_PRAGMAS,
register_my_pragma, NULL);
*/
static void
register_my_pragma (void *event_data, void *data)
{
warning (0, G_("Callback to register pragmas"));
c_register_pragma ("GCCPLUGIN", "sayhello", handle_pragma_sayhello);
}
</pre></div>
<p>It is suggested to pass <code>"GCCPLUGIN"</code> (or a short name identifying
your plugin) as the “space” argument of your pragma.
</p>
<p>Pragmas registered with <code>c_register_pragma_with_expansion</code> or
<code>c_register_pragma_with_expansion_and_data</code> support
preprocessor expansions. For example:
</p>
<div class="smallexample">
<pre class="smallexample">#define NUMBER 10
#pragma GCCPLUGIN foothreshold (NUMBER)
</pre></div>
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