1/* GLIB - Library of useful routines for C programming
2 * Copyright (C) 1995-1997 Peter Mattis, Spencer Kimball and Josh MacDonald
3 *
4 * SPDX-License-Identifier: LGPL-2.1-or-later
5 *
6 * This library is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Lesser General Public
8 * License as published by the Free Software Foundation; either
9 * version 2.1 of the License, or (at your option) any later version.
10 *
11 * This library is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 * Lesser General Public License for more details.
15 *
16 * You should have received a copy of the GNU Lesser General Public
17 * License along with this library; if not, see <http://www.gnu.org/licenses/>.
18 */
19
20/*
21 * Modified by the GLib Team and others 1997-2000. See the AUTHORS
22 * file for a list of people on the GLib Team. See the ChangeLog
23 * files for a list of changes. These files are distributed with
24 * GLib at ftp://ftp.gtk.org/pub/gtk/.
25 */
26
27#ifndef __G_MESSAGES_H__
28#define __G_MESSAGES_H__
29
30#if !defined (__GLIB_H_INSIDE__) && !defined (GLIB_COMPILATION)
31#error "Only <glib.h> can be included directly."
32#endif
33
34#include <stdarg.h>
35#include <glib/gatomic.h>
36#include <glib/gtypes.h>
37#include <glib/gmacros.h>
38#include <glib/gvariant.h>
39
40G_BEGIN_DECLS
41
42/* calculate a string size, guaranteed to fit format + args.
43 */
44GLIB_AVAILABLE_IN_ALL
45gsize g_printf_string_upper_bound (const gchar* format,
46 va_list args) G_GNUC_PRINTF(1, 0);
47
48/* Log level shift offset for user defined
49 * log levels (0-7 are used by GLib).
50 */
51#define G_LOG_LEVEL_USER_SHIFT (8)
52
53/* Glib log levels and flags.
54 */
55typedef enum
56{
57 /* log flags */
58 G_LOG_FLAG_RECURSION = 1 << 0,
59 G_LOG_FLAG_FATAL = 1 << 1,
60
61 /* GLib log levels */
62 G_LOG_LEVEL_ERROR = 1 << 2, /* always fatal */
63 G_LOG_LEVEL_CRITICAL = 1 << 3,
64 G_LOG_LEVEL_WARNING = 1 << 4,
65 G_LOG_LEVEL_MESSAGE = 1 << 5,
66 G_LOG_LEVEL_INFO = 1 << 6,
67 G_LOG_LEVEL_DEBUG = 1 << 7,
68
69 G_LOG_LEVEL_MASK = ~(G_LOG_FLAG_RECURSION | G_LOG_FLAG_FATAL)
70} GLogLevelFlags;
71
72/* GLib log levels that are considered fatal by default */
73#define G_LOG_FATAL_MASK (G_LOG_FLAG_RECURSION | G_LOG_LEVEL_ERROR)
74
75typedef void (*GLogFunc) (const gchar *log_domain,
76 GLogLevelFlags log_level,
77 const gchar *message,
78 gpointer user_data);
79
80/* Logging mechanism
81 */
82GLIB_AVAILABLE_IN_ALL
83guint g_log_set_handler (const gchar *log_domain,
84 GLogLevelFlags log_levels,
85 GLogFunc log_func,
86 gpointer user_data);
87GLIB_AVAILABLE_IN_2_46
88guint g_log_set_handler_full (const gchar *log_domain,
89 GLogLevelFlags log_levels,
90 GLogFunc log_func,
91 gpointer user_data,
92 GDestroyNotify destroy);
93GLIB_AVAILABLE_IN_ALL
94void g_log_remove_handler (const gchar *log_domain,
95 guint handler_id);
96GLIB_AVAILABLE_IN_ALL
97void g_log_default_handler (const gchar *log_domain,
98 GLogLevelFlags log_level,
99 const gchar *message,
100 gpointer unused_data);
101GLIB_AVAILABLE_IN_ALL
102GLogFunc g_log_set_default_handler (GLogFunc log_func,
103 gpointer user_data);
104GLIB_AVAILABLE_IN_ALL
105void g_log (const gchar *log_domain,
106 GLogLevelFlags log_level,
107 const gchar *format,
108 ...) G_GNUC_PRINTF (3, 4);
109GLIB_AVAILABLE_IN_ALL
110void g_logv (const gchar *log_domain,
111 GLogLevelFlags log_level,
112 const gchar *format,
113 va_list args) G_GNUC_PRINTF(3, 0);
114GLIB_AVAILABLE_IN_ALL
115GLogLevelFlags g_log_set_fatal_mask (const gchar *log_domain,
116 GLogLevelFlags fatal_mask);
117GLIB_AVAILABLE_IN_ALL
118GLogLevelFlags g_log_set_always_fatal (GLogLevelFlags fatal_mask);
119
120/* Structured logging mechanism. */
121
122/**
123 * GLogWriterOutput:
124 * @G_LOG_WRITER_HANDLED: Log writer has handled the log entry.
125 * @G_LOG_WRITER_UNHANDLED: Log writer could not handle the log entry.
126 *
127 * Return values from #GLogWriterFuncs to indicate whether the given log entry
128 * was successfully handled by the writer, or whether there was an error in
129 * handling it (and hence a fallback writer should be used).
130 *
131 * If a #GLogWriterFunc ignores a log entry, it should return
132 * %G_LOG_WRITER_HANDLED.
133 *
134 * Since: 2.50
135 */
136typedef enum
137{
138 G_LOG_WRITER_HANDLED = 1,
139 G_LOG_WRITER_UNHANDLED = 0,
140} GLogWriterOutput;
141
142/**
143 * GLogField:
144 * @key: field name (UTF-8 string)
145 * @value: field value (arbitrary bytes)
146 * @length: length of @value, in bytes, or -1 if it is nul-terminated
147 *
148 * Structure representing a single field in a structured log entry. See
149 * g_log_structured() for details.
150 *
151 * Log fields may contain arbitrary values, including binary with embedded nul
152 * bytes. If the field contains a string, the string must be UTF-8 encoded and
153 * have a trailing nul byte. Otherwise, @length must be set to a non-negative
154 * value.
155 *
156 * Since: 2.50
157 */
158typedef struct _GLogField GLogField;
159struct _GLogField
160{
161 const gchar *key;
162 gconstpointer value;
163 gssize length;
164};
165
166/**
167 * GLogWriterFunc:
168 * @log_level: log level of the message
169 * @fields: (array length=n_fields): fields forming the message
170 * @n_fields: number of @fields
171 * @user_data: user data passed to g_log_set_writer_func()
172 *
173 * Writer function for log entries. A log entry is a collection of one or more
174 * #GLogFields, using the standard [field names from journal
175 * specification](https://www.freedesktop.org/software/systemd/man/systemd.journal-fields.html).
176 * See g_log_structured() for more information.
177 *
178 * Writer functions must ignore fields which they do not recognise, unless they
179 * can write arbitrary binary output, as field values may be arbitrary binary.
180 *
181 * @log_level is guaranteed to be included in @fields as the `PRIORITY` field,
182 * but is provided separately for convenience of deciding whether or where to
183 * output the log entry.
184 *
185 * Writer functions should return %G_LOG_WRITER_HANDLED if they handled the log
186 * message successfully or if they deliberately ignored it. If there was an
187 * error handling the message (for example, if the writer function is meant to
188 * send messages to a remote logging server and there is a network error), it
189 * should return %G_LOG_WRITER_UNHANDLED. This allows writer functions to be
190 * chained and fall back to simpler handlers in case of failure.
191 *
192 * Returns: %G_LOG_WRITER_HANDLED if the log entry was handled successfully;
193 * %G_LOG_WRITER_UNHANDLED otherwise
194 *
195 * Since: 2.50
196 */
197typedef GLogWriterOutput (*GLogWriterFunc) (GLogLevelFlags log_level,
198 const GLogField *fields,
199 gsize n_fields,
200 gpointer user_data);
201
202GLIB_AVAILABLE_IN_2_50
203void g_log_structured (const gchar *log_domain,
204 GLogLevelFlags log_level,
205 ...);
206GLIB_AVAILABLE_IN_2_50
207void g_log_structured_array (GLogLevelFlags log_level,
208 const GLogField *fields,
209 gsize n_fields);
210
211GLIB_AVAILABLE_IN_2_50
212void g_log_variant (const gchar *log_domain,
213 GLogLevelFlags log_level,
214 GVariant *fields);
215
216GLIB_AVAILABLE_IN_2_50
217void g_log_set_writer_func (GLogWriterFunc func,
218 gpointer user_data,
219 GDestroyNotify user_data_free);
220
221GLIB_AVAILABLE_IN_2_50
222gboolean g_log_writer_supports_color (gint output_fd);
223GLIB_AVAILABLE_IN_2_50
224gboolean g_log_writer_is_journald (gint output_fd);
225
226GLIB_AVAILABLE_IN_2_50
227gchar *g_log_writer_format_fields (GLogLevelFlags log_level,
228 const GLogField *fields,
229 gsize n_fields,
230 gboolean use_color);
231
232GLIB_AVAILABLE_IN_2_80
233GLogWriterOutput g_log_writer_syslog (GLogLevelFlags log_level,
234 const GLogField *fields,
235 gsize n_fields,
236 gpointer user_data);
237GLIB_AVAILABLE_IN_2_50
238GLogWriterOutput g_log_writer_journald (GLogLevelFlags log_level,
239 const GLogField *fields,
240 gsize n_fields,
241 gpointer user_data);
242GLIB_AVAILABLE_IN_2_50
243GLogWriterOutput g_log_writer_standard_streams (GLogLevelFlags log_level,
244 const GLogField *fields,
245 gsize n_fields,
246 gpointer user_data);
247GLIB_AVAILABLE_IN_2_50
248GLogWriterOutput g_log_writer_default (GLogLevelFlags log_level,
249 const GLogField *fields,
250 gsize n_fields,
251 gpointer user_data);
252
253GLIB_AVAILABLE_IN_2_68
254void g_log_writer_default_set_use_stderr (gboolean use_stderr);
255GLIB_AVAILABLE_IN_2_68
256gboolean g_log_writer_default_would_drop (GLogLevelFlags log_level,
257 const char *log_domain);
258GLIB_AVAILABLE_IN_2_80
259void g_log_writer_default_set_debug_domains (const gchar * const *domains);
260
261
262/* G_MESSAGES_DEBUG enablement */
263GLIB_AVAILABLE_IN_2_72
264gboolean g_log_get_debug_enabled (void);
265GLIB_AVAILABLE_IN_2_72
266void g_log_set_debug_enabled (gboolean enabled);
267
268/**
269 * G_DEBUG_HERE:
270 *
271 * A convenience form of g_log_structured(), recommended to be added to
272 * functions when debugging. It prints the current monotonic time and the code
273 * location using %G_STRLOC.
274 *
275 * Since: 2.50
276 */
277#define G_DEBUG_HERE() \
278 g_log_structured (G_LOG_DOMAIN, G_LOG_LEVEL_DEBUG, \
279 "CODE_FILE", __FILE__, \
280 "CODE_LINE", G_STRINGIFY (__LINE__), \
281 "CODE_FUNC", G_STRFUNC, \
282 "MESSAGE", "%" G_GINT64_FORMAT ": %s", \
283 g_get_monotonic_time (), G_STRLOC)
284
285/* internal */
286void _g_log_fallback_handler (const gchar *log_domain,
287 GLogLevelFlags log_level,
288 const gchar *message,
289 gpointer unused_data);
290
291/* Internal functions, used to implement the following macros */
292GLIB_AVAILABLE_IN_ALL
293void g_return_if_fail_warning (const char *log_domain,
294 const char *pretty_function,
295 const char *expression) G_ANALYZER_NORETURN;
296GLIB_AVAILABLE_IN_ALL
297void g_warn_message (const char *domain,
298 const char *file,
299 int line,
300 const char *func,
301 const char *warnexpr) G_ANALYZER_NORETURN;
302G_NORETURN
303GLIB_DEPRECATED
304void g_assert_warning (const char *log_domain,
305 const char *file,
306 const int line,
307 const char *pretty_function,
308 const char *expression);
309
310GLIB_AVAILABLE_IN_2_56
311void g_log_structured_standard (const gchar *log_domain,
312 GLogLevelFlags log_level,
313 const gchar *file,
314 const gchar *line,
315 const gchar *func,
316 const gchar *message_format,
317 ...) G_GNUC_PRINTF (6, 7);
318
319#ifndef G_LOG_DOMAIN
320#define G_LOG_DOMAIN ((gchar*) 0)
321#endif /* G_LOG_DOMAIN */
322
323#if defined(G_HAVE_ISO_VARARGS) && !G_ANALYZER_ANALYZING
324#if defined(G_LOG_USE_STRUCTURED) && GLIB_VERSION_MAX_ALLOWED >= GLIB_VERSION_2_56
325#define g_error(...) G_STMT_START { \
326 g_log_structured_standard (G_LOG_DOMAIN, G_LOG_LEVEL_ERROR, \
327 __FILE__, G_STRINGIFY (__LINE__), \
328 G_STRFUNC, __VA_ARGS__); \
329 for (;;) ; \
330 } G_STMT_END
331#define g_message(...) g_log_structured_standard (G_LOG_DOMAIN, G_LOG_LEVEL_MESSAGE, \
332 __FILE__, G_STRINGIFY (__LINE__), \
333 G_STRFUNC, __VA_ARGS__)
334#define g_critical(...) g_log_structured_standard (G_LOG_DOMAIN, G_LOG_LEVEL_CRITICAL, \
335 __FILE__, G_STRINGIFY (__LINE__), \
336 G_STRFUNC, __VA_ARGS__)
337#define g_warning(...) g_log_structured_standard (G_LOG_DOMAIN, G_LOG_LEVEL_WARNING, \
338 __FILE__, G_STRINGIFY (__LINE__), \
339 G_STRFUNC, __VA_ARGS__)
340#define g_info(...) g_log_structured_standard (G_LOG_DOMAIN, G_LOG_LEVEL_INFO, \
341 __FILE__, G_STRINGIFY (__LINE__), \
342 G_STRFUNC, __VA_ARGS__)
343#define g_debug(...) g_log_structured_standard (G_LOG_DOMAIN, G_LOG_LEVEL_DEBUG, \
344 __FILE__, G_STRINGIFY (__LINE__), \
345 G_STRFUNC, __VA_ARGS__)
346#else
347/* for(;;) ; so that GCC knows that control doesn't go past g_error().
348 * Put space before ending semicolon to avoid C++ build warnings.
349 */
350#define g_error(...) G_STMT_START { \
351 g_log (G_LOG_DOMAIN, \
352 G_LOG_LEVEL_ERROR, \
353 __VA_ARGS__); \
354 for (;;) ; \
355 } G_STMT_END
356#define g_message(...) g_log (G_LOG_DOMAIN, \
357 G_LOG_LEVEL_MESSAGE, \
358 __VA_ARGS__)
359#define g_critical(...) g_log (G_LOG_DOMAIN, \
360 G_LOG_LEVEL_CRITICAL, \
361 __VA_ARGS__)
362#define g_warning(...) g_log (G_LOG_DOMAIN, \
363 G_LOG_LEVEL_WARNING, \
364 __VA_ARGS__)
365#define g_info(...) g_log (G_LOG_DOMAIN, \
366 G_LOG_LEVEL_INFO, \
367 __VA_ARGS__)
368#define g_debug(...) g_log (G_LOG_DOMAIN, \
369 G_LOG_LEVEL_DEBUG, \
370 __VA_ARGS__)
371#endif
372#elif defined(G_HAVE_GNUC_VARARGS) && !G_ANALYZER_ANALYZING
373#if defined(G_LOG_USE_STRUCTURED) && GLIB_VERSION_MAX_ALLOWED >= GLIB_VERSION_2_56
374#define g_error(format...) G_STMT_START { \
375 g_log_structured_standard (G_LOG_DOMAIN, G_LOG_LEVEL_ERROR, \
376 __FILE__, G_STRINGIFY (__LINE__), \
377 G_STRFUNC, format); \
378 for (;;) ; \
379 } G_STMT_END
380#define g_message(format...) g_log_structured_standard (G_LOG_DOMAIN, G_LOG_LEVEL_MESSAGE, \
381 __FILE__, G_STRINGIFY (__LINE__), \
382 G_STRFUNC, format)
383#define g_critical(format...) g_log_structured_standard (G_LOG_DOMAIN, G_LOG_LEVEL_CRITICAL, \
384 __FILE__, G_STRINGIFY (__LINE__), \
385 G_STRFUNC, format)
386#define g_warning(format...) g_log_structured_standard (G_LOG_DOMAIN, G_LOG_LEVEL_WARNING, \
387 __FILE__, G_STRINGIFY (__LINE__), \
388 G_STRFUNC, format)
389#define g_info(format...) g_log_structured_standard (G_LOG_DOMAIN, G_LOG_LEVEL_INFO, \
390 __FILE__, G_STRINGIFY (__LINE__), \
391 G_STRFUNC, format)
392#define g_debug(format...) g_log_structured_standard (G_LOG_DOMAIN, G_LOG_LEVEL_DEBUG, \
393 __FILE__, G_STRINGIFY (__LINE__), \
394 G_STRFUNC, format)
395#else
396#define g_error(format...) G_STMT_START { \
397 g_log (G_LOG_DOMAIN, \
398 G_LOG_LEVEL_ERROR, \
399 format); \
400 for (;;) ; \
401 } G_STMT_END
402
403#define g_message(format...) g_log (G_LOG_DOMAIN, \
404 G_LOG_LEVEL_MESSAGE, \
405 format)
406#define g_critical(format...) g_log (G_LOG_DOMAIN, \
407 G_LOG_LEVEL_CRITICAL, \
408 format)
409#define g_warning(format...) g_log (G_LOG_DOMAIN, \
410 G_LOG_LEVEL_WARNING, \
411 format)
412#define g_info(format...) g_log (G_LOG_DOMAIN, \
413 G_LOG_LEVEL_INFO, \
414 format)
415#define g_debug(format...) g_log (G_LOG_DOMAIN, \
416 G_LOG_LEVEL_DEBUG, \
417 format)
418#endif
419#else /* no varargs macros */
420G_NORETURN static void g_error (const gchar *format, ...) G_ANALYZER_NORETURN;
421static void g_critical (const gchar *format, ...) G_ANALYZER_NORETURN;
422
423static inline void
424g_error (const gchar *format,
425 ...)
426{
427 va_list args;
428 va_start (args, format);
429 g_logv (G_LOG_DOMAIN, G_LOG_LEVEL_ERROR, format, args);
430 va_end (args);
431
432 for(;;) ;
433}
434static inline void
435g_message (const gchar *format,
436 ...)
437{
438 va_list args;
439 va_start (args, format);
440 g_logv (G_LOG_DOMAIN, G_LOG_LEVEL_MESSAGE, format, args);
441 va_end (args);
442}
443static inline void
444g_critical (const gchar *format,
445 ...)
446{
447 va_list args;
448 va_start (args, format);
449 g_logv (G_LOG_DOMAIN, G_LOG_LEVEL_CRITICAL, format, args);
450 va_end (args);
451}
452static inline void
453g_warning (const gchar *format,
454 ...)
455{
456 va_list args;
457 va_start (args, format);
458 g_logv (G_LOG_DOMAIN, G_LOG_LEVEL_WARNING, format, args);
459 va_end (args);
460}
461static inline void
462g_info (const gchar *format,
463 ...)
464{
465 va_list args;
466 va_start (args, format);
467 g_logv (G_LOG_DOMAIN, G_LOG_LEVEL_INFO, format, args);
468 va_end (args);
469}
470static inline void
471g_debug (const gchar *format,
472 ...)
473{
474 va_list args;
475 va_start (args, format);
476 g_logv (G_LOG_DOMAIN, G_LOG_LEVEL_DEBUG, format, args);
477 va_end (args);
478}
479#endif /* !__GNUC__ */
480
481/**
482 * g_warning_once:
483 * @...: format string, followed by parameters to insert
484 * into the format string (as with printf())
485 *
486 * Logs a warning only once.
487 *
488 * g_warning_once() calls g_warning() with the passed message the first time
489 * the statement is executed; subsequent times it is a no-op.
490 *
491 * Note! On platforms where the compiler doesn't support variadic macros, the
492 * warning is printed each time instead of only once.
493 *
494 * Since: 2.64
495 */
496#if defined(G_HAVE_ISO_VARARGS) && !G_ANALYZER_ANALYZING
497#define g_warning_once(...) \
498 G_STMT_START { \
499 static int G_PASTE (_GWarningOnceBoolean, __LINE__) = 0; /* (atomic) */ \
500 if (g_atomic_int_compare_and_exchange (&G_PASTE (_GWarningOnceBoolean, __LINE__), \
501 0, 1)) \
502 g_warning (__VA_ARGS__); \
503 } G_STMT_END \
504 GLIB_AVAILABLE_MACRO_IN_2_64
505#elif defined(G_HAVE_GNUC_VARARGS) && !G_ANALYZER_ANALYZING
506#define g_warning_once(format...) \
507 G_STMT_START { \
508 static int G_PASTE (_GWarningOnceBoolean, __LINE__) = 0; /* (atomic) */ \
509 if (g_atomic_int_compare_and_exchange (&G_PASTE (_GWarningOnceBoolean, __LINE__), \
510 0, 1)) \
511 g_warning (format); \
512 } G_STMT_END \
513 GLIB_AVAILABLE_MACRO_IN_2_64
514#else
515#define g_warning_once g_warning
516#endif
517
518/**
519 * GPrintFunc:
520 * @string: the message to output
521 *
522 * Specifies the type of the print handler functions.
523 * These are called with the complete formatted string to output.
524 */
525typedef void (*GPrintFunc) (const gchar *string);
526GLIB_AVAILABLE_IN_ALL
527void g_print (const gchar *format,
528 ...) G_GNUC_PRINTF (1, 2);
529GLIB_AVAILABLE_IN_ALL
530GPrintFunc g_set_print_handler (GPrintFunc func);
531GLIB_AVAILABLE_IN_ALL
532void g_printerr (const gchar *format,
533 ...) G_GNUC_PRINTF (1, 2);
534GLIB_AVAILABLE_IN_ALL
535GPrintFunc g_set_printerr_handler (GPrintFunc func);
536
537/**
538 * g_warn_if_reached:
539 *
540 * Logs a warning.
541 *
542 * Since: 2.16
543 */
544#define g_warn_if_reached() \
545 do { \
546 g_warn_message (G_LOG_DOMAIN, __FILE__, __LINE__, G_STRFUNC, NULL); \
547 } while (0)
548
549/**
550 * g_warn_if_fail:
551 * @expr: the expression to check
552 *
553 * Logs a warning if the expression is not true.
554 *
555 * Unlike g_return_if_fail(), the expression is always evaluated, even if
556 * checks and assertions are disabled.
557 *
558 * Since: 2.16
559 */
560#define g_warn_if_fail(expr) \
561 do { \
562 if G_LIKELY (expr) ; \
563 else g_warn_message (G_LOG_DOMAIN, __FILE__, __LINE__, G_STRFUNC, #expr); \
564 } while (0)
565
566#ifdef G_DISABLE_CHECKS
567
568/**
569 * g_return_if_fail:
570 * @expr: the expression to check
571 *
572 * Verifies that the expression @expr, usually representing a precondition,
573 * evaluates to %TRUE. If the function returns a value, use
574 * g_return_val_if_fail() instead.
575 *
576 * If @expr evaluates to %FALSE, the current function should be considered to
577 * have undefined behaviour (a programmer error). The only correct solution
578 * to such an error is to change the module that is calling the current
579 * function, so that it avoids this incorrect call.
580 *
581 * To make this undefined behaviour visible, if @expr evaluates to %FALSE,
582 * the result is usually that a critical message is logged and the current
583 * function returns.
584 *
585 * If `G_DISABLE_CHECKS` is defined then the check is not performed. You
586 * should therefore not depend on any side effects of @expr.
587 *
588 * To debug failure of a g_return_if_fail() check, run the code under a debugger
589 * with `G_DEBUG=fatal-criticals` or `G_DEBUG=fatal-warnings` defined in the
590 * environment (see [Running GLib Applications](glib-running.html)):
591 *
592 * |[
593 * G_DEBUG=fatal-warnings gdb ./my-program
594 * ]|
595 *
596 * Any unrelated failures can be skipped over in
597 * [gdb](https://www.gnu.org/software/gdb/) using the `continue` command.
598 */
599#define g_return_if_fail(expr) G_STMT_START{ (void)0; }G_STMT_END
600
601/**
602 * g_return_val_if_fail:
603 * @expr: the expression to check
604 * @val: the value to return from the current function
605 * if the expression is not true
606 *
607 * Verifies that the expression @expr, usually representing a precondition,
608 * evaluates to %TRUE. If the function does not return a value, use
609 * g_return_if_fail() instead.
610 *
611 * If @expr evaluates to %FALSE, the current function should be considered to
612 * have undefined behaviour (a programmer error). The only correct solution
613 * to such an error is to change the module that is calling the current
614 * function, so that it avoids this incorrect call.
615 *
616 * To make this undefined behaviour visible, if @expr evaluates to %FALSE,
617 * the result is usually that a critical message is logged and @val is
618 * returned from the current function.
619 *
620 * If `G_DISABLE_CHECKS` is defined then the check is not performed. You
621 * should therefore not depend on any side effects of @expr.
622 *
623 * See g_return_if_fail() for guidance on how to debug failure of this check.
624 */
625#define g_return_val_if_fail(expr,val) G_STMT_START{ (void)0; }G_STMT_END
626
627/**
628 * g_return_if_reached:
629 *
630 * Logs a critical message and returns from the current function.
631 * This can only be used in functions which do not return a value.
632 *
633 * See g_return_if_fail() for guidance on how to debug failure of this check.
634 */
635#define g_return_if_reached() G_STMT_START{ return; }G_STMT_END
636
637/**
638 * g_return_val_if_reached:
639 * @val: the value to return from the current function
640 *
641 * Logs a critical message and returns @val.
642 *
643 * See g_return_if_fail() for guidance on how to debug failure of this check.
644 */
645#define g_return_val_if_reached(val) G_STMT_START{ return (val); }G_STMT_END
646
647#else /* !G_DISABLE_CHECKS */
648
649#define g_return_if_fail(expr) \
650 G_STMT_START { \
651 if (G_LIKELY (expr)) \
652 { } \
653 else \
654 { \
655 g_return_if_fail_warning (G_LOG_DOMAIN, \
656 G_STRFUNC, \
657 #expr); \
658 return; \
659 } \
660 } G_STMT_END
661
662#define g_return_val_if_fail(expr, val) \
663 G_STMT_START { \
664 if (G_LIKELY (expr)) \
665 { } \
666 else \
667 { \
668 g_return_if_fail_warning (G_LOG_DOMAIN, \
669 G_STRFUNC, \
670 #expr); \
671 return (val); \
672 } \
673 } G_STMT_END
674
675#define g_return_if_reached() \
676 G_STMT_START { \
677 g_log (G_LOG_DOMAIN, \
678 G_LOG_LEVEL_CRITICAL, \
679 "file %s: line %d (%s): should not be reached", \
680 __FILE__, \
681 __LINE__, \
682 G_STRFUNC); \
683 return; \
684 } G_STMT_END
685
686#define g_return_val_if_reached(val) \
687 G_STMT_START { \
688 g_log (G_LOG_DOMAIN, \
689 G_LOG_LEVEL_CRITICAL, \
690 "file %s: line %d (%s): should not be reached", \
691 __FILE__, \
692 __LINE__, \
693 G_STRFUNC); \
694 return (val); \
695 } G_STMT_END
696
697#endif /* !G_DISABLE_CHECKS */
698
699G_END_DECLS
700
701#endif /* __G_MESSAGES_H__ */
702

source code of include/glib-2.0/glib/gmessages.h