[Mesa-users] Segmentation fault in "Fake_glXUseXFont" (Mesa 10.4.3)

[Martin Knoblauch]

On Wed, Feb 25, 2015 at 9:17 PM, Brian Paul <brianp at vmware.com> wrote:

> On 02/25/2015 09:59 AM, Martin Knoblauch wrote:
>
>>
>>
>>
>>
>> Hi Brian,
>>
>>   so I fixed the configure option, applied the patch and rebuilt. The
>> program is now failing even quicker in:
>>
>> #0  XMesaGetCurrentDrawable () at xm_api.c:1324
>>
>> This is the only useful part of the stack and I need to omit the rest to
>> hide the innocent and incompetent ...
>>
>
> I really don't see how we'd be failing at line 1324 unless the 'front'
> pointer was garbage (which it should never be).  Can you use a debug build
> and gdb to try to narrow this down a little?
>
> I also hacked the Mesa xfont.c demo and can't reproduce a crash in
> XMesaGetCurrentDrawable().
>
> -Brian
>
>
>
Hi Brian,

 this is what gdb tells me:

1324             return front->drawable;
(gdb) list
1319    {
1320       XMesaBuffer xmbuffer = XMesaGetCurrentBuffer();
1321       if (xmbuffer) {
1322          struct xmesa_renderbuffer *front = xmbuffer->frontxrb;
1323          if (front)
1324             return front->drawable;
1325       }
1326       return 0;
1327    }
1328
(gdb) print front
$1 = (struct xmesa_renderbuffer *) 0x72c3800000030
(gdb) print front->drawable
Cannot access memory at address 0x72c38000000c0
(gdb) print *front
Cannot access memory at address 0x72c3800000030
(gdb)

Seems the "front" pointer is not-null, but not readable.

Any ideas ?

Cheers
Martin
-- 
------------------------------------------------------
Martin Knoblauch
email: k n o b i AT knobisoft DOT de
www: http://www.knobisoft.de
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