homepage

As noted in Misc/SpecialBuilds:
COUNT_ALLOCS
------------
Each type object grows three new members:
 /* Number of times an object of this type was allocated. */
 int tp_allocs;
 /* Number of times an object of this type was deallocated. */
 int tp_frees;
 /* Highwater mark: the maximum value of tp_allocs - tp_frees so
 * far; or, IOW, the largest number of objects of this type alive at
 * the same time.
 */
 int tp_maxalloc;
...
We use this for Fedora's python debug build to get some interesting debugging info. (If you try to "grep -r" through Python 3.4 source code, you'll find quite a few ifdefs with COUNT_ALLOCS.)