Up till bb3301ba the wrapper was freeing the passed strings for us. However that changed after the commit. So now we don't free any strings which results in memory leaks as reported upstream [1]: ==14265== 2,407 bytes in 1 blocks are definitely lost in loss record 1,457 of 1,550 ==14265== at 0x4C2845D: malloc (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so) ==14265== by 0x5C46624: xdr_string (in /usr/lib64/libc-2.17.so) ==14265== by 0xCFD9FCD: xdr_remote_nonnull_string (remote_protocol.c:31) ==14265== by 0xCFDC2C8: xdr_remote_domain_get_xml_desc_ret (remote_protocol.c:1617) ==14265== by 0xCFF0811: virNetMessageDecodePayload (virnetmessage.c:407) ==14265== by 0xCFE68FB: virNetClientProgramCall (virnetclientprogram.c:379) ==14265== by 0xCFBE8B1: callFull.isra.2 (remote_driver.c:6578) ==14265== by 0xCFC7F04: remoteDomainGetXMLDesc (remote_driver.c:6600) ==14265== by 0xCF8167C: virDomainGetXMLDesc (libvirt.c:4380) ==14265== by 0xCC2C4DF: libvirt_virDomainGetXMLDesc (libvirt.c:1141) ==14265== by 0x4F12B93: PyEval_EvalFrameEx (in /usr/lib64/libpython2.7.so.1.0) ==14265== by 0x4F141AC: PyEval_EvalCodeEx (in /usr/lib64/libpython2.7.so.1.0) The python documentation clearly advise us to call free() [2]. From an example in their docs: PyObject *res; char *buf = (char *) malloc(BUFSIZ); /* for I/O */ if (buf == NULL) return PyErr_NoMemory(); ...Do some I/O operation involving buf... res = PyString_FromString(buf); free(buf); /* malloc'ed */ return res; Moreover, instead of using VIR_FREE() (which we are not exporting), I'll just go with bare free(). 1: https://www.redhat.com/archives/libvir-list/2014-September/msg00736.html 2: https://docs.python.org/2/c-api/memory.html Signed-off-by: Michal Privoznik <mprivozn(a)redhat.com&gt; --- While the fix seems okay, for some reason I'm seeing another valgrind warning after the fix is applied: ==21247== Invalid read of size 4 ==21247== at 0x4EBFB93: PyObject_Free (in /usr/lib64/libpython2.7.so.1.0) ==21247== by 0x4EB613E: insertdict_by_entry (in /usr/lib64/libpython2.7.so.1.0) ==21247== by 0x4EB7BAF: dict_set_item_by_hash_or_entry (in /usr/lib64/libpython2.7.so.1.0) ==21247== by 0x4EBC4CB: _PyModule_Clear (in /usr/lib64/libpython2.7.so.1.0) ==21247== by 0x4F2916A: PyImport_Cleanup (in /usr/lib64/libpython2.7.so.1.0) ==21247== by 0x4F34B0D: Py_Finalize (in /usr/lib64/libpython2.7.so.1.0) ==21247== by 0x4F460A5: Py_Main (in /usr/lib64/libpython2.7.so.1.0) ==21247== by 0x54462BF: (below main) (in /lib64/libc-2.19.so) ==21247== Address 0x69be020 is 2,016 bytes inside a block of size 4,390 free'd ==21247== at 0x4C2B5AC: free (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so) ==21247== by 0x7F1EC2D: libvirt_virDomainGetXMLDesc (in /home/zippy/work/libvirt/libvirt-python.git/build/lib.linux-x86_64-2.7/libvirtmod.so) ==21247== by 0x4F180BB: PyEval_EvalFrameEx (in /usr/lib64/libpython2.7.so.1.0) ==21247== by 0x4F199FF: PyEval_EvalCodeEx (in /usr/lib64/libpython2.7.so.1.0) ==21247== by 0x4F18AB4: PyEval_EvalFrameEx (in /usr/lib64/libpython2.7.so.1.0) ==21247== by 0x4F199FF: PyEval_EvalCodeEx (in /usr/lib64/libpython2.7.so.1.0) ==21247== by 0x4F19AF8: PyEval_EvalCode (in /usr/lib64/libpython2.7.so.1.0) ==21247== by 0x4F32EBE: run_mod (in /usr/lib64/libpython2.7.so.1.0) ==21247== by 0x4F340E1: PyRun_FileExFlags (in /usr/lib64/libpython2.7.so.1.0) ==21247== by 0x4F352E6: PyRun_SimpleFileExFlags (in /usr/lib64/libpython2.7.so.1.0) ==21247== by 0x4F4670E: Py_Main (in /usr/lib64/libpython2.7.so.1.0) ==21247== by 0x54462BF: (below main) (in /lib64/libc-2.19.so) This happens when using our examples/dominfo.py. generator.py | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/generator.py b/generator.py index a798274..8ee046a 100755 --- a/generator.py +++ b/generator.py @@ -708,12 +708,16 @@ def print_function_wrapper(module, name, output, export, include): else: c_call = "\n c_retval = %s(%s);\n" % (name, c_call) ret_convert = " py_retval = libvirt_%sWrap((%s) c_retval);\n" % (n,c) + if n == "charPtr": + ret_convert = ret_convert + " free(c_retval);\n" ret_convert = ret_convert + " return py_retval;\n" elif ret[0] in py_return_types: (f, t, n, c) = py_return_types[ret[0]] c_return = " %s c_retval;\n" % (ret[0]) c_call = "\n c_retval = %s(%s);\n" % (name, c_call) ret_convert = " py_retval = libvirt_%sWrap((%s) c_retval);\n" % (n,c) + if n == "charPtr": + ret_convert = ret_convert + " free(c_retval);\n" ret_convert = ret_convert + " return py_retval;\n" else: if ret[0] in skipped_types: