Re: Threads Help

[Peeter Vois <Peeter Vois mail ee>]

Hi,

On 11 Dec 2002 13:01:20 +0100
Stéphane Konstantaropoulos <stephanek brutele be> wrote:

> Hello everyone,
>
> I am stuck with my GTK app.
>
> I want one callback to fire a new thread and to execute separately.
> I use pthread_create() in the callback.
>
> My problem is that when I recast the void* from the thread initial
> function into a pointer to the object I need, the pointer is NULL, and
> it segfaults when I write to it, obvious.
>
> Any ideas?
>
> Here are the bits of code that are concerned:
>
> The event to catch:
>
> static gint delete_event_cb(GtkWidget* window, GdkEventAny* e, gpointer
> data)
> {
>       lum_player_test(data);
>       return FALSE;
> }
>
> - I know the delete event is not the best one here but I need to learn
> more about events as I don't manage to catch key events yet, pfff.
>
> Here I create the new thread:
>
> void lum_player_test(gpointer player)
> {
>       pthread_create(&thread, NULL,
>                                       lum_player_play,  player);
>       return;
> }
>
> and this is the function where the thread inits:
>
> void *lum_player_play(gpointer ptr)
> {
>       LumPlayer *player = NULL;
>       player = ptr;
> [...]
>
> - And there "player" is NULL, after the cast, I tried to cast the GTK
> way or simple C way, like this
>       player = LUM_PLAYER(ptr);
> or
>       player = (LumPlayer*) ptr;
>
> But to no avail, "player" is NULL, ptr isn't though, when we enter the
> function!

I cant belive it. The ddd is good thing to investigate this. 
http://www.gnu.org/software/ddd/

> Is there a problem with shared resources? Strange, the actual "player"
> object is declared as a global variable and initialized in the main and
> never freed, so it should still be there.
>
> It is the first time I use threads in C, this is probably not the way to
> use them...
>
> I 'd like to use gthreads but I cannot find doc about them, so I stick
> to POSIX threads, this should not be the problem here.

http://developer.gnome.org/doc/API/2.0/glib/glib-Threads.html

> What do you think?
>
> BTW, this is an experiment to embed MPlayer into a gtk widget, directly.
>
> Thanks for helping,
> -- 
>    _ _ _
>   / \ \ \
>  / / \ \ \          (el greco)
>  \/_ | S  \   Muy Mano,
>   | \/    /         Muy Presa.
>    \_  K /  http://users.aber.ac.uk/ssk01
>       \  \


      Peeter Vois
http://my.tele2.ee/vois