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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?
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Valgrind is used periodically by Python developers to try to ensure there are no memory leaks or invalid memory reads/writes. If you want to use Valgrind more effectively and catch even more memory leaks, you will need to configure python --without-pymalloc.
Valgrind reports two types of issues: memory errors and memory leaks. When a program dynamically allocates memory and forgets to later free it, it creates a leak. A memory leak generally won't cause a program to misbehave, crash, or give wrong answers, and is not an urgent situation.
Specifying --vgdb-error with any value also enables --vgdb=yes , which is required for using GDB with Valgrind. Note that Valgrind provides instructions for starting GDB as well as the command to use in order to connect GDB with Valgrind.
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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