Sets the message levels which are always fatal, in any log domain.
When a message with any of these levels is logged the program terminates. You can only set the levels defined by GLib to be fatal. g_log_level_error is always fatal.
You can also make some message levels fatal at runtime by setting the `G_DEBUG` environment variable (see [Running GLib Applications]( glib-running.html)).
| fatal_mask |
the mask containing bits set for each level of error which is to be fatal |
|
the old fatal mask |