If the external thread statics are used, then
we don't need to include some C++ runtime
concepts. This refactoring moves some global initialization under
conditional compilation.
On platforms that do not support aligned mmap/VirtualAlloc,
we need to produce heavily aligned blocks to guarantee we can meet
all possible alignment requests.
This commit grabs a block much larger than requested, and then produces
"offcuts" before and after the block of smaller/same "large_classes". This
enables one mmap/virtual alloc request to services many other requests
for aligned memory.
The PAL API previously allowed for returning more memory than asked for.
This was when the PAL performed the alignment work, now this is done in
large alloc, so removing from the PAL.
Made the API so that get always returns an initialised Alloc*. Added
new fast path that doesn't perform checking, but can lead to very slow
behaviour if called and reused.
The PAL can now advertise that it supports aligned allocation. If it
does not, then the memory provider will do the alignment for it.
This change still leaves the PAL responsible for systematic testing, but
it should now be much easier to lift that out.
