(gdb) bt
#0  check_begin_texture_render (fb=0x0, ctx=0xe33e438)
    at /var/tmp/portage/media-libs/mesa-9999/work/mesa-9999/src/mesa/main/fbobject.c:2512
#1  _mesa_bind_framebuffers (ctx=0xe33e438, newDrawFb=0x0, newReadFb=0x0)
    at /var/tmp/portage/media-libs/mesa-9999/work/mesa-9999/src/mesa/main/fbobject.c:2654
#2  0xac99a3b9 in bind_framebuffer (target=target@entry=36160, framebuffer=framebuffer@entry=0, 
    allow_user_names=<optimized out>)
    at /var/tmp/portage/media-libs/mesa-9999/work/mesa-9999/src/mesa/main/fbobject.c:2607
#3  0xac99a4e2 in _mesa_BindFramebuffer (target=36160, framebuffer=0)
    at /var/tmp/portage/media-libs/mesa-9999/work/mesa-9999/src/mesa/main/fbobject.c:2677
#4  0xaca4fcbb in _mesa_unmarshal_BindFramebuffer (ctx=0xe33e438, cmd=0x9ed1b39c, cmd=0x9ed1b39c)
    at main/marshal_generated.c:17713
#5  _mesa_unmarshal_dispatch_cmd (ctx=0xe33e438, cmd=0x9ed1b39c) at main/marshal_generated.c:36903
#6  0xaca171f8 in glthread_unmarshal_batch (batch=0x9ed1b388, ctx=0xe33e438)
    at /var/tmp/portage/media-libs/mesa-9999/work/mesa-9999/src/mesa/main/glthread.c:62
#7  glthread_worker (data=0xe33e438)
    at /var/tmp/portage/media-libs/mesa-9999/work/mesa-9999/src/mesa/main/glthread.c:103
#8  0x4947e260 in start_thread (arg=0x984ffb40) at pthread_create.c:334
#9  0x493c523e in clone () at ../sysdeps/unix/sysv/linux/i386/clone.S:122