(gdb) print _PyObject_Dump(callback)

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread -1257526352 (LWP 5430)]
0xb7ea0df7 in PyFrame_New () from /usr/lib/libpython2.4.so.1.0
The program being debugged was signaled while in a function called from GDB.
GDB remains in the frame where the signal was received.
To change this behavior use "set unwindonsignal on"
Evaluation of the expression containing the function (_PyObject_Dump) will be abandoned.
(gdb)