[Python-Dev] If aligned_alloc() is missing on your platform, please let us know.

[Stefan Krah]

On Sat, Oct 28, 2017 at 03:43:47PM +1000, Nick Coghlan wrote:
> 1. CPython's own support for platforms where we don't have a native aligned
> memory allocation API to call is covered by PEP 11, so if all current
> buildbots still work, then it will be up to the folks interested in a
> platform that *doesn't* offer aligned allocations to provide both a
> suitable emulation and a buildbot to test it on.

Indeed, the feature is backed up by PEP 11.


> 2.While all of the CPython-provided memory allocators will implement the
> new slots, the folks implementing their own custom allocators will need a
> defined upgrade path in the "Porting" section of the What's New guide. For
> that, an explicit error on 3.7+ that says "Configured custom allocator
> doesn't implement aligned memory allocations" is likely going to be easier
> to debug than subtle issues with the way an implicit emulation layer
> interacts with the other memory allocator slots.
> 
> To appropriately address 2, we need more info not about which platforms
> natively support aligned memory allocations, but rather from folks that
> actually are implementing their own custom allocators. It may be that
> making the low level cross-platform raw alligned allocators available as a
> public API (independently of the switchable allocator machinery) will be a
> more appropriate way of handling that case than providing an emulation
> layer in terms of the old slots.

I don't have an opinion whether new slots should be available.  For my use
case I just need PyMem_AlignedAlloc(), PyMem_AlignedFree() that automatically
use the faster allocator for 'sizeof(void *) <= align <= ALIGNMENT' and
'size <= SMALL_REQUEST_THRESHOLD'.


So yes, it would be nice to hear from people who implement custom allocators.



Stefan Krah