[Bug target/66697] Feature request: -mstackrealign and force_align_arg_pointer for x86_64

["ubizjak at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66697

--- Comment #7 from Uroš Bizjak <ubizjak at gmail dot com> ---
Formal patch submission at [1].

Wine people, can someone please test that the patched compiler solves unaligned
stack access, as reported in WineHQ bug?

[1] https://gcc.gnu.org/ml/gcc-patches/2015-10/msg00450.html
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From: "miyuki at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/67854] Missing diagnostic for passing bool to va_arg
Date: Mon, 05 Oct 2015 17:47:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idg854

--- Comment #2 from Mikhail Maltsev <miyuki at gcc dot gnu.org> ---
(In reply to joseph@codesourcery.com from comment #1)
> I wonder if this is yet another issue with macros from system headers
> (bool being defined in a system header to expand to _Bool) ...

Looks like it is. In gimplify.c:gimplify_va_arg_expr we have:

      /* Unfortunately, this is merely undefined, rather than a constraint
         violation, so we cannot make this an error.  If this call is never
         executed, the program is still strictly conforming.  */
      warned = warning_at (loc, 0,
                           "%qT is promoted to %qT when passed through
%<...%>",
                           type, promoted_type);

And warning_at returns false. Also, for

#include <stdarg.h>
#define BOOL _Bool
void foo(va_list ap)
{
    va_arg(ap, BOOL);
}

GCC outputs:

In file included from test2.c:1:0:
test2.c: In function 'foo':
test2.c:2:14: warning: '_Bool' is promoted to 'int' when passed through '...'
 #define BOOL _Bool
              ^
test2.c:5:16: note: in expansion of macro 'BOOL'
     va_arg(ap, BOOL);
                ^
test2.c:2:14: note: (so you should pass 'int' not '_Bool' to 'va_arg')
 #define BOOL _Bool
              ^
test2.c:5:16: note: in expansion of macro 'BOOL'
     va_arg(ap, BOOL);
                ^
test2.c:2:14: note: if this code is reached, the program will abort
 #define BOOL _Bool
              ^
test2.c:5:16: note: in expansion of macro 'BOOL'
     va_arg(ap, BOOL);

IMHO, it would be more correct to output something like this:

test2.c: In function 'foo':
test2.c:5:16: warning: '_Bool' is promoted to 'int' when passed through '...'
     va_arg(ap, BOOL);
                ^
test2.c:2:14: note: expanded from macro 'BOOL'
 #define BOOL _Bool
              ^