crash from error from xcb_io.c:249

[Jim Ham]

Julien Cristau wrote:
> [cc:ing the xcb list]
>
> On Sun, Apr 11, 2010 at 14:27:38 -0700, Jim Ham wrote:
>
>> I have an application that uses direct calls to X. This application
>> worked with a previous incarnation of X (before X.org) but crashes
>> with the following message on newer versions of X. I've tried 7.4+20 and
>> 7.5+5, both Debian on a x86 machine.
>>
>> xcb_io.c:249: process_responses: Assertion `(((long)
>> (dpy->last_request_read) - (long) (dpy->request))<= 0)' failed
>>
>> Without going into a lot of detail, here's what happens:
>>
>> The main thread blocks with a the call XNextEvent(...). A secondary
>> thread sends a user event to X with XSentEvent(...). The application
>> immediately crashes on the this first call to XSendEvent with the above
>> error message. A normal event such as a mouse click generated by the
>> Xserver does not cause a crash.
>>
>> XInitThreads() is called before any other X calls. All calls to X are
>> bracketed with XLockDisplay() and XUnlockDisplay() except for the
>> XNextEvent call in the main thread. As I mentioned, the app has worked
>> for several years.
>>
>> If this is a new problem I can certainly provide more detail. The entire
>> project may be available via SVN if necessary. There is some custom
>> hardware, but a couple of patches could fix that.
>>
> Do you have a backtrace from the assertion, or an X protocol trace of
> what happens before the crash?

I've attached a zip of the output from xtrace - xtrace.log.gz. It 
appears that my app generates three user events before the crash. This 
is perfectly repeatable.

The other attachment - stdout.log - shows the commands from the command 
line, the output from my app, and the output from the xcb_io error.

Regards,

Jim
>
> Cheers,
> Julien
> _______________________________________________
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