2016-02-04 11:17 GMT+01:00 M.-A. Lemburg email@example.com:
Do you see any drawback of using pymalloc for PyMem_Malloc()?
Yes: You cannot free memory allocated using pymalloc with the standard C lib free().
That's not completly new.
If Python is compiled in debug mode, you get a fatal error with a huge error message if you free the memory allocated by PyMem_Malloc() using PyObject_Free() or PyMem_RawFree().
But yes, technically it's possible to use free() when Python is *not* compiled in debug mode.
It would be better to go through the list of PyMem_*() calls in Python and replace them with PyObject_*() calls, where possible.
There are 536 calls to the functions PyMem_Malloc(), PyMem_Realloc() and PyMem_Free().
I would prefer to modify a single place having to replace 536 calls :-/
Does anyone recall the rationale to have two families to memory allocators?
The PyMem_*() APIs were needed to have a cross-platform malloc() implementation which returns standard C lib free()able memory, but also behaves well when passing 0 as size.
Yeah, PyMem_Malloc() & PyMem_Free() help to have a portable behaviour. But, why not PyObject_Malloc() & PObject_Free() were not used in the first place?
An explanation can be that PyMem_Malloc() can be called without the GIL held. But it wasn't true before Python 3.4, since PyMem_Malloc() called (indirectly) PyObject_Malloc() when Python was compiled in debug mode, and PyObject_Malloc() requires the GIL to be held.
When I wrote the PEP 445, there was a discussion about the GIL. It was proposed to allow to call PyMem_xxx() without the GIL: https://www.python.org/dev/peps/pep-0445/#gil-free-pymem-malloc
This option was rejected.