[PATCH] FreeGLUT causes segfault in recent Xorg GL driver

[Michel Dänzer]

On Mon, 2008-11-10 at 10:31 +0100, Florian Echtler wrote:
> 
> I've just switched to a recent Xorg build (git checkout from last
> Friday). I'm using the radeon driver on a Radeon Mobility X1400, and
> GLUT-based applications run with 3D acceleration when I start them with
> the GLUT implementation from MESA. However, when I try freeglut rev. 749
> instead (just by replacing the libraries), the following happens:
> 
> Program received signal SIGSEGV, Segmentation fault.
> ...
> (gdb) bt
> #0  0xb61df5a2 in driBindContext (context=0xb390ff40, draw=0x0, 
>   read=0x0) at dri_glx.c:457
> #1  0xb61be38a in MakeContextCurrent (dpy=0x83d8438, draw=54525954, 
>   read=54525954, gc=0xb3903530, pre13=0) at glxcurrent.c:391
> #2  0xb534ead2 in fgOpenWindow () from /usr/lib/libglut.so.3
> #3  0xb534ce05 in fgCreateWindow () from /usr/lib/libglut.so.3
> #4  0xb534e1fa in glutCreateWindow () from /usr/lib/libglut.so.3
> ...
> (gdb) 
> 
> Same backtrace occurs with a freshly compiled Freeglut test program.
> 
> I managed to fix this bug with the following one-line patch:
> 
> --- src/freeglut_window.c	(Revision 749)
> +++ src/freeglut_window.c	(Arbeitskopie)
> @@ -759,10 +759,9 @@
>      XSetWMProtocols( fgDisplay.Display, window->Window.Handle,
>                       &fgDisplay.DeleteWindow, 1 );
>  
> -    glXMakeContextCurrent(
> +    glXMakeCurrent(
>          fgDisplay.Display,
>          window->Window.Handle,
> -        window->Window.Handle,
>          window->Window.Context
>      );
>  
> Unfortunately, I don't know a) which side effects this might have (from 
> looking at the macro, it seems that there shouldn't be any) and b) I'm 
> also unsure whether this patch is appropriate for older X releases.
> 
> So I'd be glad if some of you could have a quick look whether this is 
> really a fix or rather just an ugly workaround.

glXMakeContextCurrent() is only available as of GLX version 1.3, but the
drivers you're using only support GLX version 1.2. So this does look
like a freeglut bug. That said, it should probably be handled more
gracefully...


-- 
Earthling Michel Dänzer           |          http://tungstengraphics.com
Libre software enthusiast         |          Debian, X and DRI developer