generator: Free strings after libvirt_charPtrWrap

https://bugzilla.redhat.com/show_bug.cgi?id=1140998

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@redhat.com>

1 files changed, 4 insertions, 0 deletions

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: