Warning and debug in Gnome technology

</pre><h3 style="">g_warning()</h3><pre class="programlisting" style="">#define             g_warning(...)

A convenience function/macro to log a warning message.

You can make warnings fatal at runtime by setting the 

G_DEBUG

 environment variable (see Running
GLib Applications).

If 

g_log_default_handler()

 is
used as the log handler function, a newline character will automatically be appended to @..., and need not be entered manually.

Parameters

...	format string, followed by parameters to insert into the format string (as with  printf() )

We get a negative errno-style error code named "r". And then we can write the code like this.

g_warning ("Error doing something blah: %s", g_strerror (-r));

Debug and critical are almost the same as the warning.

Here are the API of g_debug and g_critical.

g_debug()

#define             g_debug(...)

A convenience function/macro to log a debug message.

If 

g_log_default_handler()

 is
used as the log handler function, a new-line character will automatically be appended to @..., and need not be entered manually.

Such messages are suppressed by the 

g_log_default_handler()

 unless
the G_MESSAGES_DEBUG environment variable is set appropriately.

Parameters

...	format string, followed by parameters to insert into the format string (as with  printf() )

g_critical()

#define             g_critical(...)

Logs a "critical warning" (G_LOG_LEVEL_CRITICAL). It's more or less application-defined
what constitutes a critical vs. a regular warning. You could call 

g_log_set_always_fatal()

 to
make critical warnings exit the program, then use 

g_critical()

 for
fatal errors, for example.

You can also make critical warnings fatal at runtime by setting the 

G_DEBUG

 environment variable (see Running
GLib Applications).

If 

g_log_default_handler()

 is
used as the log handler function, a new-line character will automatically be appended to @..., and need not be entered manually.

Parameters

...	format string, followed by parameters to insert into the format string (as with  printf() )