TempAlloc review starts now

[Lutger Blijdestijn]

dsimcha wrote:

> == Quote from Steven Schveighoffer (schveiguy at yahoo.com)'s article
>> alignedMalloc:
>> I seriously question having such a feature.  According to my C++ book
>> malloc returns a pointer "suitably aligned for any type".  According to
>> Microsoft, malloc is 16-byte aligned (of course, D doesn't use
>> microsoft's
>> runtime, DMC doesn't seem to identify alignment in malloc docs).  GNU
>> appears to guarantee 8-byte alignment on 32-bit systems, 16 on 64-bit
>> systems (making this function mostly useless on 64-bit dmd).
>> There are also some posix functions that align a malloc to a requested
>> size (see memalign).
> 
> I definitely need it in the implementation of TempAlloc, so it's gonna be
> there but it can be made private if there's a consensus that it's not
> needed in the public API.
> 
>> At the very least, the function should identify what the alignment is if
>> you *don't* use it.  I'd like to see a good use case for this feature in
>> an example, otherwise, I think it should be killed.
> 
> The alignment if you don't use it depends on the C malloc function for
> your
> platform.  A use case might be if you need 16-byte aligned arrays to use
> SSE instructions, but that's hard to demonstrate in a short example.

Maybe it would be more broadly useful if the alignment could be specified, 
turning it into a portable version of posix_memalign?

http://pubs.opengroup.org/onlinepubs/009695399/functions/posix_memalign.html 

It's not my domain and use cases may be niche, but it does fit the systems 
language aspect of D.