[Bug c/71255] Implement #pragma may_alias

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71255

--- Comment #26 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
(In reply to Florian Weimer from comment #22)
> (In reply to Marek Polacek from comment #21)
> > The testcase in Comment 14 should now compile fine.
> 
> What's the best way to detect that a compiler has this fix?  We cannot use a
> configure check.  Is there anything better than looking at __GNUC__?  Are
> you going to backport this fix?  Thanks.

I'm not planning on backporting this, so I think the best way is to check
__GNUC__ > 7.

Now, I'm kind of flummoxed.  Is there any need for the new pragma anymore?  The
other C testcase in Comment 16 compiles without warnings I think.  I wouldn't
want to spend time implementing a new #pragma that is useless ;).