glib/gmessages.h

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