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Re: Does malloc tell us anything about alignment modulo k?
Geert Bosch wrote:
> We're having a lot of trouble with this for Ada as well.
Definitely. And not only with malloc (see below).
> Probably there should be a separate MALLOC_ALIGNMENT definition
> in GCC.
Probably.
What would for sure help a whole lot is to have a precise description of what
expectations are set regarding various alignment related configuration macros
and what is supposed to happen (work/not-work/be-rejected) in extreme
situations.
Some bits are already documented. Some are not and raise questions IMHO.
As a single instance, are there rules about how BIGGEST_ALIGNMENT and
STACK_BOUNDARY should relate ? It seems not, according to the doc and to
various actual target configurations.
It then appears that some alignment requests (up to BIGGEST_ALIGNMENT)
are not guaranteed to be honored for stack objects when STACK_BOUNDARY
< BIGGEST_ALIGNMENT. Isn't that a problem ? It is a very typical one for
Ada.