Is it normal that running python under valgrind shows many errors with memory?

python debugging memory-leaks valgrind python-c-extension
bialix picture bialix · Oct 5, 2009 · Viewed 7.3k times · Source

I've tried to debug memory crash in my Python C extension and tried to run script under valgrind. I found there is too much "noise" in the valgrind output, even if I've ran simple command as:

valgrind python -c ""

Valgrind output full of repeated info like this:

==12317== Invalid read of size 4
==12317==    at 0x409CF59: PyObject_Free (in /usr/lib/libpython2.5.so.1.0)
==12317==    by 0x405C7C7: PyGrammar_RemoveAccelerators (in /usr/lib/libpython2.5.so.1.0)
==12317==    by 0x410A1EC: Py_Finalize (in /usr/lib/libpython2.5.so.1.0)
==12317==    by 0x4114FD1: Py_Main (in /usr/lib/libpython2.5.so.1.0)
==12317==    by 0x8048591: main (in /usr/bin/python2.5)
==12317==  Address 0x43CD010 is 7,016 bytes inside a block of size 8,208 free'd
==12317==    at 0x4022F6C: free (in /usr/lib/valgrind/x86-linux/vgpreload_memcheck.so)
==12317==    by 0x4107ACC: PyArena_Free (in /usr/lib/libpython2.5.so.1.0)
==12317==    by 0x41095D7: PyRun_StringFlags (in /usr/lib/libpython2.5.so.1.0)
==12317==    by 0x40DF262: (within /usr/lib/libpython2.5.so.1.0)
==12317==    by 0x4099569: PyCFunction_Call (in /usr/lib/libpython2.5.so.1.0)
==12317==    by 0x40E76CC: PyEval_EvalFrameEx (in /usr/lib/libpython2.5.so.1.0)
==12317==    by 0x40E70F3: PyEval_EvalFrameEx (in /usr/lib/libpython2.5.so.1.0)
==12317==    by 0x40E896A: PyEval_EvalCodeEx (in /usr/lib/libpython2.5.so.1.0)
==12317==    by 0x40E8AC2: PyEval_EvalCode (in /usr/lib/libpython2.5.so.1.0)
==12317==    by 0x40FD99C: PyImport_ExecCodeModuleEx (in /usr/lib/libpython2.5.so.1.0)
==12317==    by 0x40FFC93: (within /usr/lib/libpython2.5.so.1.0)
==12317==    by 0x41002B0: (within /usr/lib/libpython2.5.so.1.0)

Python 2.5.2 on Slackware 12.2.

Is it normal behavior? If so then valgrind maybe is inappropriate tool for debugging memory errors in Python?

Answer

Nick Craig-Wood picture Nick Craig-Wood · Oct 5, 2009

You could try using the suppression file that comes with the python source

Reading the Python Valgrind README is a good idea too!

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