[Pixman] [PATCH] test/utils.c: Make the stack unaligned only on 32 bit Windows

Søren Sandmann sandmann at cs.au.dk
Mon Nov 18 09:00:11 PST 2013

John Emmas <johne53 at tiscali.co.uk> writes:

> I'm not sure if there's a connection here or if it's just a
> coincidence but in a completely separate library (libffi) I noticed a
> very recent commit by Mark Kettenis (6th Nov 2013) which he describes
> as "Align the stack pointer to 16-bytes".  Unfortunately, his change
> is in an assembly language module which I cant profess to understand.
> Is anyone here qualified to check the git log for libffi to find out
> if Mark's arrived at the same flawed conclusion about stack alignment
> or if (in his case) there's a valid reason for setting 16-byte
> alignment?

If that commit is making libffi make calls with a 16-byte aligned stack
pointer, that's a good change since GCC compiled functions seems to be
expecting that in many cases.

Whether GCC *should* be expecting that is debatable (and I think the
answer is definitely "no" on Windows), but there is no harm in libffi
meeting those expectations, whether reasonable or not.


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