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<h3 class="section">23.6 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>The <code>PLUGIN_ATTRIBUTES</code> callback is called during attribute
registration. Use the <code>register_attribute</code> function to register
custom attributes.
<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, handle_user_attribute, false };
/* 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>
<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><span class="file">c-family/c-pragma.h</span></samp>.
<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>
<p>It is suggested to pass <code>"GCCPLUGIN"</code> (or a short name identifying
your plugin) as the “space” argument of your pragma.
<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:
<pre class="smallexample"> #define NUMBER 10
#pragma GCCPLUGIN foothreshold (NUMBER)
</pre>
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