> It doesn't happen with bytearrays, so I suspect it's that you only
> DECREF when releasebuffer method exists:

Thanks, that was indeed the problem; this is now fixed in r65683 and r65685.

My initial observation that test_unicode leaks a lot of memory was
incorrect - it's rather that test_raiseMemError consumes all my
memory (probably without leaking).

test_unicode still leaks 6 references each time; one reference is leaked
whenever a SyntaxError is raised. I'm not sure though whether this was
caused by this patch, so I'll close this issue as fixed. Any further
improvements should be done through separate patches (without my
involvement, most likely).