1 @c Copyright (c) 2009 Free Software Foundation, Inc.
2 @c Free Software Foundation, Inc.
3 @c This is part of the GCC manual.
4 @c For copying conditions, see the file gcc.texi.
10 @section Loading Plugins
12 Plugins are supported on platforms that support @option{-ldl
13 -rdynamic}. They are loaded by the compiler using @code{dlopen}
14 and invoked at pre-determined locations in the compilation
17 Plugins are loaded with
19 @option{-fplugin=/path/to/NAME.so} @option{-fplugin-arg-NAME-<key1>[=<value1>]}
21 The plugin arguments are parsed by GCC and passed to respective
22 plugins as key-value pairs. Multiple plugins can be invoked by
23 specifying multiple @option{-fplugin} arguments.
28 Plugins are activated by the compiler at specific events as defined in
29 @file{gcc-plugin.h}. For each event of interest, the plugin should
30 call @code{register_callback} specifying the name of the event and
31 address of the callback function that will handle that event.
33 The header @file{gcc-plugin.h} must be the first gcc header to be included.
35 @subsection Plugin license check
37 Every plugin should define the global symbol @code{plugin_is_GPL_compatible}
38 to assert that it has been licensed under a GPL-compatible license.
39 If this symbol does not exist, the compiler will emit a fatal error
40 and exit with the error message:
43 fatal error: plugin <name> is not licensed under a GPL-compatible license
44 <name>: undefined symbol: plugin_is_GPL_compatible
45 compilation terminated
48 The type of the symbol is irrelevant. The compiler merely asserts that
49 it exists in the global scope. Something like this is enough:
52 int plugin_is_GPL_compatible;
55 @subsection Plugin initialization
57 Every plugin should export a function called @code{plugin_init} that
58 is called right after the plugin is loaded. This function is
59 responsible for registering all the callbacks required by the plugin
60 and do any other required initialization.
62 This function is called from @code{compile_file} right before invoking
63 the parser. The arguments to @code{plugin_init} are:
66 @item @code{plugin_info}: Plugin invocation information.
67 @item @code{version}: GCC version.
70 The @code{plugin_info} struct is defined as follows:
73 struct plugin_name_args
75 char *base_name; /* Short name of the plugin
76 (filename without .so suffix). */
77 const char *full_name; /* Path to the plugin as specified with
79 int argc; /* Number of arguments specified with
81 struct plugin_argument *argv; /* Array of ARGC key-value pairs. */
82 const char *version; /* Version string provided by plugin. */
83 const char *help; /* Help string provided by plugin. */
87 If initialization fails, @code{plugin_init} must return a non-zero
88 value. Otherwise, it should return 0.
90 The version of the GCC compiler loading the plugin is described by the
94 struct plugin_gcc_version
97 const char *datestamp;
100 const char *configuration_arguments;
104 The function @code{plugin_default_version_check} takes two pointers to
105 such structure and compare them field by field. It can be used by the
106 plugin's @code{plugin_init} function.
109 @subsection Plugin callbacks
111 Callback functions have the following prototype:
114 /* The prototype for a plugin callback function.
115 gcc_data - event-specific data provided by GCC
116 user_data - plugin-specific data provided by the plug-in. */
117 typedef void (*plugin_callback_func)(void *gcc_data, void *user_data);
120 Callbacks can be invoked at the following pre-determined events:
126 PLUGIN_PASS_MANAGER_SETUP, /* To hook into pass manager. */
127 PLUGIN_FINISH_TYPE, /* After finishing parsing a type. */
128 PLUGIN_FINISH_UNIT, /* Useful for summary processing. */
129 PLUGIN_CXX_CP_PRE_GENERICIZE, /* Allows to see low level AST in C++ FE. */
130 PLUGIN_FINISH, /* Called before GCC exits. */
131 PLUGIN_INFO, /* Information about the plugin. */
132 PLUGIN_GGC_START, /* Called at start of GCC Garbage Collection. */
133 PLUGIN_GGC_MARKING, /* Extend the GGC marking. */
134 PLUGIN_GGC_END, /* Called at end of GGC. */
135 PLUGIN_REGISTER_GGC_ROOTS, /* Register an extra GGC root table. */
136 PLUGIN_ATTRIBUTES, /* Called during attribute registration */
137 PLUGIN_EVENT_LAST /* Dummy event used for indexing callback
143 To register a callback, the plugin calls @code{register_callback} with
147 @item @code{char *name}: Plugin name.
148 @item @code{enum plugin_event event}: The event code.
149 @item @code{plugin_callback_func callback}: The function that handles @code{event}.
150 @item @code{void *user_data}: Pointer to plugin-specific data.
153 For the PLUGIN_PASS_MANAGER_SETUP, PLUGIN_INFO, and
154 PLUGIN_REGISTER_GGC_ROOTS pseudo-events the @code{callback} should be
155 null, and the @code{user_data} is specific.
157 @section Interacting with the pass manager
159 There needs to be a way to add/reorder/remove passes dynamically. This
160 is useful for both analysis plugins (plugging in after a certain pass
161 such as CFG or an IPA pass) and optimization plugins.
163 Basic support for inserting new passes or replacing existing passes is
164 provided. A plugin registers a new pass with GCC by calling
165 @code{register_callback} with the @code{PLUGIN_PASS_MANAGER_SETUP}
166 event and a pointer to a @code{struct plugin_pass} object defined as follows
169 enum pass_positioning_ops
171 PASS_POS_INSERT_AFTER, // Insert after the reference pass.
172 PASS_POS_INSERT_BEFORE, // Insert before the reference pass.
173 PASS_POS_REPLACE // Replace the reference pass.
178 struct opt_pass *pass; /* New pass provided by the plugin. */
179 const char *reference_pass_name; /* Name of the reference pass for hooking
181 int ref_pass_instance_number; /* Insert the pass at the specified
182 instance number of the reference pass. */
183 /* Do it for every instance if it is 0. */
184 enum pass_positioning_ops pos_op; /* how to insert the new pass. */
188 /* Sample plugin code that registers a new pass. */
190 plugin_init (struct plugin_name_args *plugin_info,
191 struct plugin_gcc_version *version)
193 struct plugin_pass pass_info;
197 /* Code to fill in the pass_info object with new pass information. */
201 /* Register the new pass. */
202 register_callback (plugin_info->base_name, PLUGIN_PASS_MANAGER_SETUP, NULL, &pass_info);
209 @section Interacting with the GCC Garbage Collector
211 Some plugins may want to be informed when GGC (the GCC Garbage
212 Collector) is running. They can register callbacks for the
213 @code{PLUGIN_GGC_START} and @code{PLUGIN_GGC_END} events (for which
214 the callback is called with a null @code{gcc_data}) to be notified of
215 the start or end of the GCC garbage collection.
217 Some plugins may need to have GGC mark additional data. This can be
218 done by registering a callback (called with a null @code{gcc_data})
219 for the @code{PLUGIN_GGC_MARKING} event. Such callbacks can call the
220 @code{ggc_set_mark} routine, preferably thru the @code{ggc_mark} macro
221 (and conversely, these routines should usually not be used in plugins
222 outside of the @code{PLUGIN_GGC_MARKING} event).
224 Some plugins may need to add extra GGC root tables, e.g. to handle
225 their own @code{GTY}-ed data. This can be done with the
226 @code{PLUGIN_REGISTER_GGC_ROOTS} pseudo-event with a null callback and
227 the extra root table as @code{user_data}. Running the @code{gengtype
228 -p @var{source-dir} @var{file-list} @var{plugin*.c} ...} utility
229 generates this extra root table.
231 You should understand the details of memory management inside GCC
232 before using @code{PLUGIN_GGC_MARKING} or
233 @code{PLUGIN_REGISTER_GGC_ROOTS}.
236 @section Giving information about a plugin
238 A plugin should give some information to the user about itself. This
239 uses the following structure:
249 Such a structure is passed as the @code{user_data} by the plugin's
250 init routine using @code{register_callback} with the
251 @code{PLUGIN_INFO} pseudo-event and a null callback.
253 @section Registering custom attributes
255 For analysis purposes it is useful to be able to add custom attributes.
257 The @code{PLUGIN_ATTRIBUTES} callback is called during attribute
258 registration. Use the @code{register_attribute} function to register
262 /* Attribute handler callback */
264 handle_user_attribute (tree *node, tree name, tree args,
265 int flags, bool *no_add_attrs)
270 /* Attribute definition */
271 static struct attribute_spec user_attr =
272 @{ "user", 1, 1, false, false, false, handle_user_attribute @};
274 /* Plugin callback called during attribute registration.
275 Registered with register_callback (plugin_name, PLUGIN_ATTRIBUTES, register_attributes, NULL)
278 register_attributes (void *event_data, void *data)
280 warning (0, G_("Callback to register attributes"));
281 register_attribute (&user_attr);
287 @section Building GCC plugins
289 If plugins are enabled, GCC installs the headers needed to build a
290 plugin (somehwere in the installation tree, e.g. under
291 @file{/usr/local}). In particular a @file{plugin/include} directory
292 is installed, containing all the header files needed to build plugins.
294 On most systems, you can query this @code{plugin} directory by
295 invoking @command{gcc -print-file-name=plugin} (replace if needed
296 @command{gcc} with the appropriate program path).
298 The following GNU Makefile excerpt shows how to build a simple plugin:
302 PLUGIN_SOURCE_FILES= plugin1.c plugin2.c
303 PLUGIN_OBJECT_FILES= $(patsubst %.c,%.o,$(PLUGIN_SOURCE_FILES))
304 GCCPLUGINS_DIR:= $(shell $(GCC) -print-file-name=plugin)
305 CFLAGS+= -I$(GCCPLUGINS_DIR)/include -fPIC -O2
307 plugin.so: $(PLUGIN_OBJECT_FILES)
308 $(GCC) -shared $^ -o $@
311 A single source file plugin may be built with @code{gcc -I`gcc
312 -print-file-name=plugin`/include -fPIC -shared -O2 plugin.c -o
313 plugin.so}, using backquote shell syntax to query the @file{plugin}
316 Plugins needing to use @command{gengtype} require a GCC build
317 directory for the same version of GCC that they will be linked