Re: [Caml-list] Tips to find the cause of a seg fault

[Philippe Veber <philippe.veber@googlemail.com>]

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2010/12/1 <oliver@first.in-berlin.de>

> On Wed, Dec 01, 2010 at 11:26:19AM +0100, Philippe Veber wrote:
> > 2010/12/1 <oliver@first.in-berlin.de>
> >
> > > Hi,
> > >
> > >
> > > On Wed, Dec 01, 2010 at 09:32:16AM +0100, Philippe Veber wrote:
> > > > Actually I was not confident I could extract a small program
> reproducing
> > > the
> > > > issue until ... you had me try ! I could get a very tiny example that
> > > > behaves exactly the same, which does not involve opengl at all, only
> sdl.
> > > > Here it is :
> > > [...]
> > >
> > >
> > > After installing some sdl-related packages, I could comopile the code.
> > > So far it does not crash.
> > >
> > > What actions do create the segfault for you?
> > >
> >
> > roll the mouse wheel up or down fast with the cursor on the window.
> However,
> > I know that this problem does not occur everywhere, so you might well
> > observe nothing ...
> [...]
>
> No crash happened.
>
>
> Normally I'm very gifted to crash software.... by just looking at it.
>
> If there is a bug, it will find me  ;)
>
> Did you tried another X-driver?
>
> In your valgrind printout there was mentioned "libnvidia".
> And a crash seems to have been occured at that part:
>
>
> > ==11306==    by 0x4215D5: camlHum__entry (in
> > /home/pveber/hum/_build/src/hum.native)
> > ==11306==    by 0xC5767A7: ???
> > ==11306==
> > ==11306== Conditional jump or move depends on uninitialised value(s)
> > ==11306==    at 0x7695580: ??? (in
> > /usr/lib/nvidia-current/libnvidia-glcore.so.260.19.06)
> > ==11306==    by 0x1000000000000: ???
> > ==11306==
> > vex amd64->IR: unhandled instruction bytes: 0xFF 0xD8 0xC 0xF9 0xFF 0xD8
> > ==11306== valgrind: Unrecognised instruction at address 0x4992cb.
> > ==11306== Your program just tried to execute an instruction that Valgrind
>
>
> So, please chack this. Maybe one of the free drivers does work better,
> or maybe an update could help.
>
> If you update your kernel, then you might also need to update the
> X-drivers, because the nvidia stuff is non-free binary stuff,
> and maybe some bindings don't work correctly with a new kernel.
>
>
> I once experienced problems the other way around: crashing blender
> with the free drivers, just by scaling into a view more and more,
> and no crash with the non-free drivers.
>
> This X11-driver part is really a desert...
>
> ...and even if you don't use OpenGL commands... the driver that you
> installed
> and configured will be used nevretheless, and if there is something wrong,
> you
> will get your crashes.
>
> Look if the X11-driver-bindings are all up to date for the driver you use
> now,
>
they are.


> and also try another X11-driver...
>
I sure will.

The thing is in my last example, there is no warning from the nvidia driver
anymore, so I'd think the bug must be in the sdl part. I should also check
if this doesn't come from the touchpad driver, using a real mouse on the
same system.
Anyway thanks for your comments !

ph.

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