Re: checking status of GString

[Owen Taylor <otaylor redhat com>]

Aaron Walker <amwalker@gate.net> writes:

> I have a callback that is called when I exit the main window:
> 
> void main_destroy_cb (GtkWidget *widget, GWindow *gfind)
> {
>     g_string_free(gfind->cmd, TRUE);
>     g_free(gfind->entry);
>     g_free(gfind);
>     gtk_main_quit();
> }
> 
> The GString gfind->cmd is initialize in the function that calls this
> callback, which means that on exit, my program is assuming that
> gfind->cmd has been initialized.  I thought that this would work to
> check it:
> 
> if(gfind->cmd != NULL)
>     g_string_free(gfind->cmd, TRUE);
> 
> which didn't work, so I tried:
> 
> if(gfind->cmd->str != NULL)
>     g_string_free(gfind->cmd, TRUE);
> 
> which also did not work (segfaults).
> 
> I am trying to avoid initializing the GString right away, to prevent
> this.  I would just like to check if it is null or not.

Well, you need to remember that if you create a structure
with malloc() or g_new(), the fields of the structure will
not be initialized to NULL. You need to do this explicitely
yourself. Alternatively, you can use the functions 
g_malloc0() and g_new0() to zero out the memory when it
is allocated. 

[ Actually, assumming that NULL will have a bit-pattern of
  all zeros is not standard ANSI C, though it works
  universally on the platforms where GTK+ runs. ]

Regards,
                                        Owen