Re: Can someone help me get rid of XLib errors? please

[Tim Flechtner <timf trdlnk com>]

if you grab a mutex lock around your gtk_main, then try to acquire the 
lock from within a call back (presumably executed by the gtk loop), 
won't you deadlock (the lock has already been acquired, and not yet 
released)?

-tim

Douglas Ian Linder wrote:
> >  When i run my gtk app, sometimes to program crashes because of an Xlib 
> >  error. Now i know this has to do with thread synchronization, and I
> >  heard that only 1 thread can access gtk functions at a time. So i went 
> >  online, and I found an example which used pthreads. and that noted 
> >  just to use gdk_thread_init, at the and gdk_thread_enter and 
> >  gdk_thread_leave before and after gtk_main, respectively. While this 
> >  method compiled, I get an immediate Segmentation fault as soon as I 
> >  run  my program. Currently, I only use gdb as a debugger, and that
> >  hasn't helped. any ideas to beat this Xlib problem? thanks!
>
>
> Umm...Have you had a look at the api docs on the gtk_thread_XXX functions?
>
> I'm not totally familiar with the gtk functions, but it looks pretty
> straight forward (threads are pretty easy). Basically gtk keeps a set
> of mutex locks, and you have to manually manage them.
>
> To start with you need to lock gtk_main() with a gtk_thread_enter() /
> gtk_thread_leave() around it. However, you also need to perform a 
> similar lock around each access to gtk functions in your callbacks...
>
> Segmentation fault sounds like you're not initialising properly.
> Are you sure you've :
>
> g_thread_init (NULL);
> gdk_threads_init ();
> gtk_init (&argc, &argv);
>
> If you have, check your callbacks: Are you sure you're locking around
> any calls to gtk functions? (ie. gtk_thread_enter() and gtk_thread_leave()
> around ANY call to gtk in call backs)...
>
> The documentation is pretty um...basic. You might want to think about
> using gtk_main_interation_do() with the lock/unlock around it if you
> want to do fancy things like move where you're event processing is
> taking place around.
>
> Anyway, hope that helps. If not you'll have to be more specific in your
> question.
>
> ciao,
> Doug.
>
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