Version:           valgrind-3.5.0-Debian (using Devel)
Compiler:          g++ (Ubuntu 4.4.1-4ubuntu8) 4.4.1 
OS:                Linux
Installed from:    Compiled sources

The OS is Ubuntu 9.10 (Linux x 2.6.31-14-generic #48-Ubuntu SMP Fri Oct 16 14:04:26 UTC 2009 i686 GNU/Linux).

I ran valgrind 3.5.0 using this command line:

valgrind --trace-children=yes --read-var-info=yes --num-callers=20  --suppressions=icu.supp --suppressions=valgrind-python.supp --tool=exp-ptrcheck  myprogram myprogramoptions

The output ended in:

sysno == 331
exp-ptrcheck: the 'impossible' happened:
   unhandled syscall
==6146==    at 0x38014460: report_and_quit (m_libcassert.c:145)
==6146==    by 0x380144B6: panic (m_libcassert.c:227)
==6146==    by 0x38014507: vgPlain_tool_panic (m_libcassert.c:242)
==6146==    by 0x3800270E: h_post_syscall (h_main.c:2536)
==6146==    by 0x38054AC9: vgPlain_post_syscall (syswrap-main.c:1678)
==6146==    by 0x380556CA: vgPlain_client_syscall (syswrap-main.c:1576)
==6146==    by 0x38051AC2: handle_syscall (scheduler.c:872)
==6146==    by 0x38052BFE: vgPlain_scheduler (scheduler.c:1068)
==6146==    by 0x3807EC24: run_a_thread_NORETURN (syswrap-linux.c:91)

sched status:
  running_tid=1

Thread 1: status = VgTs_Runnable
==6146==    at 0x4155886: pipe2 (in /lib/tls/i686/cmov/libc-2.10.1.so)
==6146==    by 0x40F5699: popen@@GLIBC_2.1 (iopopen.c:312)
==6146==    by 0x813E2E4: ??? (in /usr/bin/python2.6)
==6146==    by 0x80DC0CF: PyEval_EvalFrameEx (in /usr/bin/python2.6)
==6146==    by 0x80DDDF1: PyEval_EvalCodeEx (in /usr/bin/python2.6)
==6146==    by 0x80DC1B3: PyEval_EvalFrameEx (in /usr/bin/python2.6)
==6146==    by 0x80DD383: PyEval_EvalFrameEx (in /usr/bin/python2.6)
==6146==    by 0x80DD383: PyEval_EvalFrameEx (in /usr/bin/python2.6)
==6146==    by 0x80DDDF1: PyEval_EvalCodeEx (in /usr/bin/python2.6)
==6146==    by 0x80DDEF6: PyEval_EvalCode (in /usr/bin/python2.6)
==6146==    by 0x80FAA1E: PyRun_FileExFlags (in /usr/bin/python2.6)
==6146==    by 0x80FAC11: PyRun_SimpleFileExFlags (in /usr/bin/python2.6)
==6146==    by 0x805C8D7: Py_Main (in /usr/bin/python2.6)
==6146==    by 0x805BAEA: main (in /usr/bin/python2.6)