I modified PyMem_Malloc() to use the pymalloc allocator in the issue #26249. This change helped to find a memory leak in test_format that I introduced in Python 3.6:
http://bugs.python.org/issue26249#msg264174

This memory leak gave me an idea: PyMem_RawMalloc() should also update sys.getallocatedblocks() (number of currently allocated blocks). It would help to find memory leaks using "python -m test -R 3:3" in extension modules using PyMem_RawMalloc() (and not PyMem_Malloc() or PyObject_Malloc()).

Attached patch uses an atomic variable _Py_AllocatedBlocks, but only in debug mode. I chose to only change the variable in debug mode to:

* not impact performances
* I don't know if atomic variables are well supported (especially the "var++" operation)
* I don't know yet the impact of this change (how sys.getallocatedblocks() is used).

(The patch would be simpler if the release mode would also be impacted.)

The patch changes _PyObject_Alloc() and _PyObject_Free() in debug mode to only account allocations directly made by pymalloc, to let PyMem_RawMalloc() and PyMem_RawFree() update the _Py_AllocatedBlocks variable. In release mode, _PyObject_Alloc() and _PyObject_Free() are responsible to update the _Py_AllocatedBlocks variable for allocations delegated to PyMem_RawMalloc() and PyMem_RawFree().