[Mesa-dev] [PATCH 2/2] gallium/util: libunwind support

[Rob Clark]

On Mon, Apr 3, 2017 at 4:57 PM, Rob Clark <robdclark at gmail.com> wrote:
> On Mon, Apr 3, 2017 at 4:06 PM, Thomas Hellstrom <thellstrom at vmware.com> wrote:
>> On 04/03/2017 07:33 PM, Thomas Hellstrom wrote:
>>> On 04/03/2017 07:13 PM, Rob Clark wrote:
>>>> On Mon, Apr 3, 2017 at 12:56 PM, Thomas Hellstrom <thellstrom at vmware.com> wrote:
>>>>> Hi, Rob,
>>>>>
>>>>> On 03/24/2017 10:21 PM, Rob Clark wrote:
>>>>>> It's kinda sad that (a) we don't have debug_backtrace support on !X86
>>>>>> and that (b) we re-invent our own crude backtrace support in the first
>>>>>> place.  If available, use libunwind instead.  The backtrace format is
>>>>>> based on what xserver and weston use, since it is nice not to have to
>>>>>> figure out a different format.
>>>>>>
>>>>>> Signed-off-by: Rob Clark <robdclark at gmail.com>
>>>>> Did you consider glibc "backtrace()", I think it's also available on ARM...
>>>> I had not.. although xserver and weston are already using libunwind.
>>>> I'm not sure about portability of libunwind to other libc
>>>> implementations (but I guess it is at least not worse than using a
>>>> glibc specific API).
>>>>
>>>> I suppose we could always add a fallback to backtrace().
>>>>
>> Hmm. This commit (bisected) appears to break svga/vmwgfx in DEBUG mode:
>>
>> *** Error in `glxgears': malloc(): memory corruption: 0x00000000025c09c0 ***
>> Aborted (core dumped)
>>
>> The svga linux winsys makes extensive use of the backtrace functionality
>> using u_debug_flush.c
>
> ok, I can reproduce.. hopefully patch following shortly..
>

So, I found one other minor issue, but the big problem is
debug_stack_frame size difference, because u_debug_flush.c doesn't
#include config.h..  adding:

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

in u_debug_stack.h solves that..  although I think usually folks
prefer to have that in .c files.  (Not sure if I remember the reason.)

So we should either add that in u_debug_stack.h or track down all the
.c files that #include it and add there.

(Or is there a reason we don't just do -include config.h globally in
the build system?)

BR,
-R