I can't reproduce this here, but it may be something unique about your system.

I believe that commit you reference fixes this bug (which I have seen before) rather than creates it. Are you sure you're running master and have rebuilt from scratch (by deleting the "build" directory before rebuilding)? If you're certain of that, have you tried building either of the parent commits of that commit to confirm that it works before and not after?

i can reproduce with matplotlib-1.1.1 and without -DNDEBUG. the git master actually seems to works.

it is confusing, because a fix was committed back in 2010 with:

b5ce842

but later on was overwritten with the commit refered in the first comment.

I see. Thanks for the additional info. I'll look at the 1.1.x branch and see what I can discover there.

The fix in b5ce842 was no longer needed following an update to PyCXX.

Strangely, I'm still unable to reproduce on 1.1.1 without -NDEBUG:

CFLAGS=-UNDEBUG python setup.py install

This sometimes happens when things don't get fully rebuilt after switching branches.

CXXFLAGS need to be set as well

Thanks -- just tried that. Due to a bug in how distutils handles CXXFLAGS, it doesn't actually matter, but for good measure it makes sense. Unfortunately, I'm still not able to reproduce.

What platform are you on?

i am on gentoo x86_64, but i did check on ubuntu 12.04 x86_64 to make sure it was not distro specific.
to reproduce from a vanilla matplotlib-1.1.1 tar ball, i do:

CXXFLAGS=-UNDEBUG CFLAGS=-UNDEBUG python setup.py build
cp doc/matplotlibrc .
PYTHONPATH=build/lib.linux-x86_64-2.7 python examples/pylab_examples/stix_fonts_demo.py

Right you are. The missing piece was the matplotlibrc from the doc directory.

With debugging turned on, it looks like those ob_refcnt-- operations are required on both 1.1.x and master. Thanks for finding this. Without debugging turned on, these are probably silently leaking.