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Functions
void | g_print () |
GPrintFunc | g_set_print_handler () |
void | (*GPrintFunc) () |
void | g_printerr () |
GPrintFunc | g_set_printerr_handler () |
#define | g_return_if_fail() |
#define | g_return_val_if_fail() |
#define | g_return_if_reached |
#define | g_return_val_if_reached() |
#define | g_warn_if_fail() |
#define | g_warn_if_reached |
void | g_on_error_query () |
void | g_on_error_stack_trace () |
#define | G_BREAKPOINT |
Functions
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, without
appending a trailing new-line character. Typically, format
should end with
its own new-line character.
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()
, g_log_structured()
, or the convenience macros 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, without appending
a trailing new-line character. Typically, format
should end with its own
new-line character.
g_printerr() should not be used from within libraries.
Instead g_log()
or g_log_structured()
should be used, or the convenience
macros 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)
Verifies that the expression expr
, usually representing a precondition,
evaluates to TRUE
. If the function returns a value, use
g_return_val_if_fail()
instead.
If expr
evaluates to FALSE
, the current function should be considered to
have undefined behaviour (a programmer error). The only correct solution
to such an error is to change the module that is calling the current
function, so that it avoids this incorrect call.
To make this undefined behaviour visible, if expr
evaluates to FALSE
,
the result is usually that a critical message is logged and the current
function returns.
If G_DISABLE_CHECKS
is defined then the check is not performed. You
should therefore not depend on any side effects of expr
.
To debug failure of a g_return_if_fail()
check, run the code under a debugger
with G_DEBUG=fatal-criticals
or G_DEBUG=fatal-warnings
defined in the
environment (see Running GLib Applications):
1 |
G_DEBUG=fatal-warnings gdb ./my-program |
Any unrelated failures can be skipped over in
gdb using the continue
command.
g_return_val_if_fail()
#define g_return_val_if_fail(expr,val)
Verifies that the expression expr
, usually representing a precondition,
evaluates to TRUE
. If the function does not return a value, use
g_return_if_fail()
instead.
If expr
evaluates to FALSE
, the current function should be considered to
have undefined behaviour (a programmer error). The only correct solution
to such an error is to change the module that is calling the current
function, so that it avoids this incorrect call.
To make this undefined behaviour visible, if expr
evaluates to FALSE
,
the result is usually that a critical message is logged and val
is
returned from the current function.
If G_DISABLE_CHECKS
is defined then the check is not performed. You
should therefore not depend on any side effects of expr
.
See g_return_if_fail()
for guidance on how to debug failure of this check.
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.
See g_return_if_fail()
for guidance on how to debug failure of this check.
g_return_val_if_reached()
#define g_return_val_if_reached(val)
Logs a critical message and returns val
.
See g_return_if_fail()
for guidance on how to debug failure of this check.
g_warn_if_fail()
#define g_warn_if_fail(expr)
Logs a warning if the expression is not true.
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.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 |
#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 "[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.
Parameters
prg_name |
the program name, needed by gdb for the "[S]tack trace"
option. If |
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. You can get the current process's program name
with g_get_prgname()
, assuming that you have called gtk_init()
or
gdk_init()
.
This function may cause different actions on non-UNIX platforms.