[Xquartz-dev] Help requested debugging rgl under XQuartz

Wed Feb 24 09:11:59 PST 2021

I don't see any calls to __stack_chk_fail .  It's possible I 
misinterpreted what was going on after the IOAccelGLContextClearDrawable 
call.  I'll take another look.

Duncan Murdoch

On 24/02/2021 11:41 a.m., Jeremy Huddleston Sequoia wrote:
> __stack_chk_guard is part of stack protector.
> 
> If it's not liking the value in __stack_chk_guard, it means the stack 
> was smashed.
> 
> When this is detected, the compiler runtime should 
> call __stack_chk_fail() if implemented or abort if not.  Given that 
> we're not crashing, I wonder if there's a handler somewhere that ends up 
> causing us to return the bad value instead of crashing.
> 
> Can you break on __stack_chk_fail and see if that gives us anything useful?
> 
> 
> 
> 
>> On Feb 24, 2021, at 06:26, Duncan Murdoch <murdoch.duncan at gmail.com 
>> <mailto:murdoch.duncan at gmail.com>> wrote:
>>
>> Tracing in with lldb, it appears to be this sequence of calls leading 
>> to the 10005 error value:
>>
>> r
>>  * frame #0: 0x00007fff5afc19e0 
>> libGPUSupportMercury.dylib`gldAttachDrawable + 1
>>    frame #1: 0x00007fff4467f396 GLEngine`gliAttachDrawableWithOptions 
>> + 251
>>    frame #2: 0x00007fff4465d9f5 
>> OpenGL`___lldb_unnamed_symbol40$$OpenGL + 972
>>    frame #3: 0x00007fff446618e2 
>> OpenGL`___lldb_unnamed_symbol59$$OpenGL + 82
>>    frame #4: 0x00007fff44661c29 OpenGL`CGLSetSurface + 330
>>    frame #5: 0x00007fff70c6ca63 
>> libXplugin.1.dylib`xp_attach_gl_context + 95
>>    frame #6: 0x0000000108590dee libGL.1.dylib`surface_make_current + 206
>>    frame #7: 0x000000010858df6a 
>> libGL.1.dylib`apple_glx_make_current_context + 1274
>>    frame #8: 0x0000000108574579 libGL.1.dylib`applegl_bind_context + 185
>>    frame #9: 0x000000010856237e libGL.1.dylib`MakeContextCurrent + 414
>>    frame #10: 0x00000001085621d9 libGL.1.dylib`glXMakeCurrent + 41
>>
>>
>> The libGPUSupportMercury.dylib`gldAttachDrawable function calls
>>
>> IOAccelGLContextClearDrawable
>>
>> then does some sort of check of __stack_chk_guard and doesn't like 
>> what it sees, and sets the error.
>>
>> Does this give any hint about what's wrong, or a way to fix it?
>>
>> Duncan Murdoch
>>
>>
>>
>> On 23/02/2021 4:31 p.m., Duncan Murdoch wrote:
>>> On 23/02/2021 3:47 p.m., Jeremy Huddleston Sequoia wrote:
>>>>
>>>>
>>>>> On Feb 23, 2021, at 06:14, Duncan Murdoch <murdoch.duncan at gmail.com 
>>>>> <mailto:murdoch.duncan at gmail.com>
>>>>> <mailto:murdoch.duncan at gmail.com 
>>>>> <mailto:murdoch.duncan at gmail.com>>> wrote:
>>>>>
>>>>> On 23/02/2021 12:47 a.m., Jeremy Huddleston Sequoia wrote:
>>>>>>> On Feb 22, 2021, at 14:38, Duncan Murdoch 
>>>>>>> <murdoch.duncan at gmail.com <mailto:murdoch.duncan at gmail.com>
>>>>>>> <mailto:murdoch.duncan at gmail.com 
>>>>>>> <mailto:murdoch.duncan at gmail.com>> 
>>>>>>> <mailto:murdoch.duncan at gmail.com <mailto:murdoch.duncan at gmail.com>
>>>>>>> <mailto:murdoch.duncan at gmail.com 
>>>>>>> <mailto:murdoch.duncan at gmail.com>>>> wrote:
>>>>>>>
>>>>>>> I've made a little bit of progress.
>>>>>>>
>>>>>>> The message "error: xp_attach_gl_context returned: 2" comes from the
>>>>>>> Mesa routine surface_make_current, which calls xp_attach_gl_context.
>>>>>>>  I haven't found where xp_attach_gl_context is defined.
>>>>>> xp_attach_gl_context is in libXplugin (check Xplugin.h in the SDK).
>>>>>> 2 is XP_BadValue, which is returned if cgl_ctx is NULL... so I'd
>>>>>> suggest looking into why mesa is calling xp_attach_gl_context with a
>>>>>> NULL context.
>>>>>
>>>>> Thanks, that's helpful.  The context is not NULL, so I need to think
>>>>> of other ways it could be "bad".
>>>>
>>>> Ok, well xp_attach_gl_context is just a wrapper around CGLSetSurface(),
>>>> which is an internal function to do exactly what we're trying to do
>>>> here.  If it returns any error, xp_attach_gl_context returns bad value.
>>>>
>>>> Are you able to capture this in the debugger and figure out what the
>>>> return value from CGLSetSurface() is?  That will tell us what the
>>>> underlying CGLError is, which might help shed some light on this.
>>> I believe it's returning  0x0000000000002715 when there's an error.
>>> That's 10005, kCGLBadDrawable.  So now I need to find out what happened
>>> to the drawable.
>>> This feels like progress!  Thanks again.
>>> Duncan
>>>>
>>>>> Here's what I see with LIBGL_DIAGNOSTIC=1.  For a successful open,
>>>>>
>>>>>> rgl.open()
>>>>> function is no-op
>>>>> Debug     ../src/glx/apple/apple_glx_context.c:205
>>>>> apple_glx_create_context(4295810496): apple_glx_create_context: ac
>>>>> 0x100a10a00 ac->context_obj 0x107cdce00
>>>>> 2021-02-23 08:23:00.041711-0500 R[45754:1283995]
>>>>> apple_glx_create_context: ac 0x100a10a00 ac->context_obj 0x107cdce00
>>>>> Debug     ../src/glx/apple/apple_glx_drawable.c:342
>>>>> apple_glx_drawable_create(4295810496): apple_glx_drawable_create: new
>>>>> drawable 0x107ce0e00
>>>>> 2021-02-23 08:23:00.042235-0500 R[45754:1283995]
>>>>> apple_glx_drawable_create: new drawable 0x107ce0e00
>>>>> Debug     ../src/glx/apple/apple_glx_surface.c:154
>>>>> create_surface(4295810496): create_surface: created a surface for
>>>>> drawable 0x600066 with uid 621
>>>>> 2021-02-23 08:23:00.044773-0500 R[45754:1283995] create_surface:
>>>>> created a surface for drawable 0x600066 with uid 621
>>>>> Debug     ../src/glx/apple/apple_glx_surface.c:69
>>>>> surface_make_current(4295810496): surface_make_current:
>>>>> ac->context_obj 0x107cdce00 s->surface_id 9
>>>>> 2021-02-23 08:23:00.044839-0500 R[45754:1283995] surface_make_current:
>>>>> ac->context_obj 0x107cdce00 s->surface_id 9
>>>>> Debug     ../src/glx/apple/apple_glx_surface.c:89
>>>>> surface_make_current(4295810496): surface_make_current: drawable 
>>>>> 0x600066
>>>>> 2021-02-23 08:23:00.045680-0500 R[45754:1283995] surface_make_current:
>>>>> drawable 0x600066
>>>>> ... (more lines deleted)
>>>>>
>>>>> After I run quartz(), I see this:
>>>>>
>>>>>> rgl.open()
>>>>> Debug     ../src/glx/apple/apple_glx_context.c:205
>>>>> apple_glx_create_context(4295810496): apple_glx_create_context: ac
>>>>> 0x10262bb00 ac->context_obj 0x1058c4800
>>>>> 2021-02-23 08:23:35.666675-0500 R[45754:1283995]
>>>>> apple_glx_create_context: ac 0x10262bb00 ac->context_obj 0x1058c4800
>>>>> Debug     ../src/glx/apple/apple_glx_drawable.c:342
>>>>> apple_glx_drawable_create(4295810496): apple_glx_drawable_create: new
>>>>> drawable 0x107648000
>>>>> 2021-02-23 08:23:35.667040-0500 R[45754:1283995]
>>>>> apple_glx_drawable_create: new drawable 0x107648000
>>>>> Debug     ../src/glx/apple/apple_glx_surface.c:154
>>>>> create_surface(4295810496): create_surface: created a surface for
>>>>> drawable 0x6000c9 with uid 629
>>>>> 2021-02-23 08:23:35.669119-0500 R[45754:1283995] create_surface:
>>>>> created a surface for drawable 0x6000c9 with uid 629
>>>>> Debug     ../src/glx/apple/apple_glx_surface.c:69
>>>>> surface_make_current(4295810496): surface_make_current:
>>>>> ac->context_obj 0x1058c4800 s->surface_id 13
>>>>> 2021-02-23 08:23:35.669195-0500 R[45754:1283995] surface_make_current:
>>>>> ac->context_obj 0x1058c4800 s->surface_id 13
>>>>> error: xp_attach_gl_context returned: 2
>>>>> Debug     ../src/glx/applegl_glx.c:60
>>>>> applegl_bind_context(4295810496): applegl_bind_context: error YES
>>>>> 2021-02-23 08:23:35.669834-0500 R[45754:1283995] applegl_bind_context:
>>>>> error YES
>>>>>
>>>>> and then I get my own messages from the failure of glXMakeCurrent().
>>>>>  As far as I can see, everything appears fine until the call to
>>>>> xp_attach_gl_context.
>>>>>
>>>>>
>>>>> Everything looks very similar up to the failure of
>>>>> xp_attach_gl_context.  Any idea I why the value returned a few lines
>>>>> earlier from apple_glx_create_context() should be a bad value?
>>>>>
>>>>> Duncan Murdoch
>>>>>
>>>>>
>>>>
>>
> 