Nathaniel: "(...) and numpy won't necessarily use this API anyway."

Can you elaborate why numpy wouldn't use this new API? I designed it with numpy in mind :-)

Using PyMem_AlignedAlloc() instead of using directly posix_memalign()/_aligned_alloc() provides the debug features for free:

* tracemalloc is able to trace memory allocations
* detect buffer underflow
* detect buffer overflow
* detect API misuse like PyMem_Free(PyMem_AlignedAlloc()) -- it doesn't detect free(PyMem_AlignedAlloc()) which is plain wrong on Windows (but this one should crash immediately ;-))

Other advantages:

* PyMem_AlignedAlloc(alignment, 0) is well defined: it never returns NULL
* PyMem_AlignedAlloc(alignment, size) checks on alignment value are the same on all operating systems

Moreover, Python takes care of the portability for you :-)