> The test case finds some leak in 3.3 too, it seems.

3.3 should be much better since it uses mmap() and munmap() to manage the object allocator's arenas (unless this is disabled under OS X for some reason, that is).

Here under Linux:

$ python3.3 testiterbug.py 
3.3.0b1 (default:1d811e1097ed, Jul 29 2012, 20:20:37) 
[GCC 4.5.2]

[row for row in iterit(16777216)]
Memory usage:   7.8 MB

[row for row in iterit(8388608)]
Memory usage:   7.8 MB