X server testing

[Mark Kettenis]

> Date: Thu, 18 Jun 2009 17:07:02 +1000
> From: Peter Hutterer <peter.hutterer at who-t.net>
> 
> > (gdb) bt
> > #0  0x0086b422 in __kernel_vsyscall ()
> > #1  0x002d46d0 in raise () from /lib/tls/i686/cmov/libc.so.6
> > #2  0x002d6098 in abort () from /lib/tls/i686/cmov/libc.so.6
> > #3  0x0031224d in ?? () from /lib/tls/i686/cmov/libc.so.6
> > #4  0x00318604 in ?? () from /lib/tls/i686/cmov/libc.so.6
> > #5  0x0031a5b6 in free () from /lib/tls/i686/cmov/libc.so.6
> > #6  0x080a7a61 in Xfree (ptr=0x0) at ../../os/utils.c:1159
> > #7  0x08129420 in ProcessOtherEvent (ev=0x944e298, device=0xbec2d38) at ../../Xi/exevents.c:953
> > #8  0x08151ec8 in ProcessPointerEvent (ev=0x944e298, mouse=0xbec2d38) at ../../xkb/xkbAccessX.c:732
> > #9  0x0809fb05 in mieqProcessDeviceEvent (dev=0xbec2d38, event=0x944e298, screen=0x0) at ../../mi/mieq.c:403
> > #10 0x081056b8 in ProcXTestFakeInput (client=<value optimized out>) at ../../Xext/xtest.c:418
> > #11 0x0806cf87 in Dispatch () at ../../dix/dispatch.c:426
> > #12 0x080674b5 in main (argc=10, argv=0xbff73ac4, envp=0xbff73af0) at ../../dix/main.c:283
> > (gdb) print ev->any.type == ET_Raw
> > $11 = 1
> > (gdb)
> 
> Xfree shouldn't crash on NULL pointers, we might actually have some memory
> corruption happening. Does valgrind complain about anything?

This backtrace doesn't necessarily mean Xfree was called with a NULL
pointer as its argument.  The origional function argument may have
been modified, and GCC doesn't always generate enough debug
information to inidcate that this happened.