http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54130
--- Comment #11 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-08-01
09:28:43 UTC ---
(In reply to comment #10)
> (In reply to comment #9)
> > I realize that several (not all) of the things discussed here assume that
> > functions returning bool and int are binary compatible, which is likely
> > true on
> > most platforms but there might be exceptions.
>
> It's not true on x86_64 - return values are not extended to word_mode thus
> you may have garbage in the upper parts of %eax for bool.
Testcase:
_Bool foo (_Bool *p)
{
return *p;
}
compile at -Os and get
foo:
.LFB0:
.cfi_startproc
movb (%rdi), %al
ret
which I believe at least preserves %ah (not sure about bits 16 .. 32).
