g_print ()

void                g_print                             (const gchar *format,
                                                         ...);

Outputs a formatted message via the print handler. The default print handler simply outputs the message to stdout.

g_print() should not be used from within libraries for debugging messages, since it may be redirected by applications to special purpose message windows or even files. Instead, libraries should use g_log(), or the convenience functions g_message(), g_warning() and g_error().

g_set_print_handler ()

GPrintFunc          g_set_print_handler                 (GPrintFunc func);

Sets the print handler. Any messages passed to g_print() will be output via the new handler. The default handler simply outputs the message to stdout. By providing your own handler you can redirect the output, to a GTK+ widget or a log file for example.

GPrintFunc ()

void                (*GPrintFunc)                       (const gchar *string);

Specifies the type of the print handler functions. These are called with the complete formatted string to output.

g_printerr ()

void                g_printerr                          (const gchar *format,
                                                         ...);

Outputs a formatted message via the error message handler. The default handler simply outputs the message to stderr.

g_printerr() should not be used from within libraries. Instead g_log() should be used, or the convenience functions g_message(), g_warning() and g_error().

g_set_printerr_handler ()

GPrintFunc          g_set_printerr_handler              (GPrintFunc func);

Sets the handler for printing error messages. Any messages passed to g_printerr() will be output via the new handler. The default handler simply outputs the message to stderr. By providing your own handler you can redirect the output, to a GTK+ widget or a log file for example.

g_return_if_fail()

#define             g_return_if_fail(expr)

Returns from the current function if the expression is not true. If the expression evaluates to FALSE, a critical message is logged and the function returns. This can only be used in functions which do not return a value.

g_return_val_if_fail()

#define             g_return_val_if_fail(expr,val)

Returns from the current function, returning the value val, if the expression is not true. If the expression evaluates to FALSE, a critical message is logged and val is returned.

g_return_if_reached

#define             g_return_if_reached()

Logs a critical message and returns from the current function. This can only be used in functions which do not return a value.

g_return_val_if_reached()

#define             g_return_val_if_reached(val)

Logs a critical message and returns val.

g_warn_if_fail()

#define             g_warn_if_fail(expr)

Logs a warning if the expression is not true.

Since 2.16

g_warn_if_reached

#define             g_warn_if_reached()

Logs a critical warning.

Since 2.16

g_on_error_query ()

void                g_on_error_query                    (const gchar *prg_name);

Prompts the user with [E]xit, [H]alt, show [S]tack trace or [P]roceed. This function is intended to be used for debugging use only. The following example shows how it can be used together with the g_log() functions.

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#include <glib.h>
static void
log_handler (const gchar   *log_domain,
         GLogLevelFlags log_level,
         const gchar   *message,
         gpointer       user_data)
{
  g_log_default_handler (log_domain, log_level, message, user_data);
  g_on_error_query (MY_PROGRAM_NAME);
}
int main (int argc, char *argv[])
{
  g_log_set_handler (MY_LOG_DOMAIN,
             G_LOG_LEVEL_WARNING |
                     G_LOG_LEVEL_ERROR |
                     G_LOG_LEVEL_CRITICAL,
             log_handler,
             NULL);
 /* ... */

If [E]xit is selected, the application terminates with a call to _exit(0).

If [H]alt is selected, the application enters an infinite loop. The infinite loop can only be stopped by killing the application, or by setting glib_on_error_halt to FALSE (possibly via a debugger).

If [S]tack trace is selected, g_on_error_stack_trace() is called. This invokes gdb, which attaches to the current process and shows a stack trace. The prompt is then shown again.

If [P]roceed is selected, the function returns.

This function may cause different actions on non-UNIX platforms.

g_on_error_stack_trace ()

void                g_on_error_stack_trace              (const gchar *prg_name);

Invokes gdb, which attaches to the current process and shows a stack trace. Called by g_on_error_query() when the [S]tack trace option is selected.

This function may cause different actions on non-UNIX platforms.

G_BREAKPOINT

#  define G_BREAKPOINT()        G_STMT_START{ __asm__ __volatile__ ("int $03"); }G_STMT_END

Inserts a breakpoint instruction into the code. On x86 and alpha systems this is implemented as a soft interrupt and on other architectures it raises a SIGTRAP signal.