Bug 795002

Description of problem:
I've been writing an experimental static analysis tool to detect bugs commonly occurring within C Python extension modules:
  https://fedorahosted.org/gcc-python-plugin/
  http://gcc-python-plugin.readthedocs.org/en/latest/cpychecker.html
  http://fedoraproject.org/wiki/Features/StaticAnalysisOfPythonRefcounts

I ran the latest version of the tool (in git master; post 0.9) on
net-snmp-5.7.1-4.fc17.src.rpm, and it reports various errors.

You can see a list of errors here, triaged into categories (from most significant to least significant):
http://fedorapeople.org/~dmalcolm/gcc-python-plugin/2012-02-18/net-snmp-5.7.1-4.fc17/

I've manually reviewed the issues reported by the tool.

Within the category "Reference leak within initialization" the 1 issue reported looks inconsequential

Within the category "Segfaults within error-handling paths" the first issue reported:
  netsnmp/client_intf.c:py_netsnmp_attr_set_string:dereferencing NULL (val_obj->ob_refcnt) at netsnmp/client_intf.c:1190
looks like a genuine bug: this could segfault under low-memory conditions (where the call to Py_BuildValue() fails and returns NULL).

The other two bugs are similar, but PyInt_FromLong() is unlikely to fail (it will always succeed for the range -5..255); if the numbers are more negative that than, it could segfault in the same way.


Within the category "Returning (PyObject*)NULL without setting an exception" the 1 issue reported looks like a false positive.


There may of course be other bugs in my checker tool.

Hope this is helpful; let me know if you need help reading the logs that the tool generates - I know that it could use some improvement.

Version-Release number of selected component (if applicable):
net-snmp-5.7.1-4.fc17
gcc-python-plugin post-0.9 git 771455b3128b1323e80bdda53939d8d140a84c68 running the checker in an *f16* chroot