Hi, We observed the program was cored dump. And examing the core file, we found the call stack: #0 0x00007f26487e6b82 in rpyvmprof_f_pypy_rrr () from /usr/local/pypy/libpypy-c.so #1 0x00007f26494a797a in rpyvmprof_t_pypy_rrr () from /usr/local/pypy/libpypy-c.so #2 0x00007f26487a1ad4 in pypy_g_appexec___src__glob___________________import_sys () from /usr/local/pypy/libpypy-c.so #3 0x00007f26486f980b in pypy_g.pypy_execute_source () from /usr/local/pypy/libpypy-c.so #4 0x00007f26486f9994 in pypy_g_pypy_execute_source_ptr () from /usr/local/pypy/libpypy-c.so #5 0x00007f26484e6f42 in pypy_execute_source_ptr () from /usr/local/pypy/libpypy-c.so #6 0x00007f26484e6d82 in pypy_execute_source () from /usr/local/pypy/libpypy-c.so ... And debugging the core file, the char* buffer passed to pypy_execute_source() was: (gdb) print pyExBuffer $1 = "import sys\nsys.path.insert(0,'job_runtime/lib/python2.7/site-packages/udf')\000/1440989742122"... The code was to add a directory to sys.path(). The error was not reproduceable by extracting the piece of code from the whole programme, and I've no ideas why the segmentation fault happened. Does anyone knows what the function "rpyvmprof_f_pypy_rrr ()" did? And are there any methods to debug and found out the cause?