From: Richard Biener <richard.guenther@gmail.com>
To: Michael Matz <matz@suse.de>
Cc: Alexander Monakov <amonakov@ispras.ru>,
Paul Eggert <eggert@cs.ucla.edu>,
Jonathan Wakely <jwakely.gcc@gmail.com>,
Aaron Ballman <aaron@aaronballman.com>,
Zack Weinberg <zack@owlfolio.org>,
c-std-porting@lists.linux.dev, autoconf@gnu.org,
gcc@gcc.gnu.org, cfe-commits@lists.llvm.org,
Gnulib bugs <bug-gnulib@gnu.org>
Subject: Re: How can Autoconf help with the transition to stricter compilation defaults?
Date: Wed, 16 Nov 2022 16:27:32 +0100 [thread overview]
Message-ID: <CAFiYyc2RwHLA+HQWWZk069G3-2xA6-i0E_n1mMpAcNA_g7n3Qw@mail.gmail.com> (raw)
In-Reply-To: <alpine.LSU.2.20.2211161445070.5466@wotan.suse.de>
On Wed, Nov 16, 2022 at 4:02 PM Michael Matz via Gcc <gcc@gcc.gnu.org> wrote:
>
> Hey,
>
> On Wed, 16 Nov 2022, Alexander Monakov wrote:
>
> > > The idea is so obvious that I'm probably missing something, why autoconf
> > > can't use that idiom instead. But perhaps the (historic?) reasons why it
> > > couldn't be used are gone now?
> >
> > Ironically, modern GCC and LLVM optimize '&foobar != 0' to '1' even at -O0,
> > and thus no symbol reference remains in the resulting assembly.
>
> Err, right, *head-->table*.
> Playing with volatile should help:
>
> char foobar(void);
> char (* volatile ptr)(void);
> int main(void) {
> ptr = foobar;
> return ptr != 0;
> }
using printf for foobar this works even with GCC 2.95.2 and with trunk
and -Wall diagnoses
t.c:1:6: warning: conflicting types for built-in function 'printf';
expected 'int(const char *, ...)' [-Wbuiltin-declaration-mismatch]
1 | char printf(void);
| ^~~~~~
t.c:1:1: note: 'printf' is declared in header '<stdio.h>'
+++ |+#include <stdio.h>
1 | char printf(void);
so without -Werror this should be fine.
Richard.
>
>
> Ciao,
> Michael.
next prev parent reply other threads:[~2022-11-16 15:27 UTC|newest]
Thread overview: 65+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-10 17:16 Zack Weinberg
2022-11-10 17:52 ` Nick Bowler
2022-11-10 17:58 ` Jonathan Wakely
2022-11-10 18:12 ` Jonathan Wakely
2022-11-10 18:44 ` Aaron Ballman
2022-11-12 2:56 ` Zack Weinberg
2022-11-10 18:05 ` Rich Felker
2022-11-10 21:44 ` Florian Weimer
2022-11-12 3:22 ` Zack Weinberg
2022-11-10 18:08 ` Florian Weimer
2022-11-12 3:40 ` Zack Weinberg
2022-11-12 3:43 ` Sam James
2022-11-12 14:27 ` Zack Weinberg
2022-11-12 3:45 ` Joseph Myers
2022-11-12 15:59 ` Wookey
2022-11-12 16:12 ` Zack Weinberg
2022-11-10 18:19 ` Aaron Ballman
2022-11-10 21:05 ` Paul Eggert
2022-11-11 15:11 ` Aaron Ballman
2022-11-13 0:43 ` Paul Eggert
2022-11-14 12:41 ` Aaron Ballman
2022-11-14 18:14 ` Paul Eggert
2022-11-14 18:30 ` Florian Weimer
2022-11-14 18:35 ` Aaron Ballman
2022-11-15 14:50 ` Jonathan Wakely
2022-11-15 19:08 ` Paul Eggert
2022-11-15 19:27 ` Jonathan Wakely
2022-11-15 20:27 ` Paul Eggert
2022-11-15 20:57 ` Aaron Ballman
2022-11-15 23:09 ` Paul Eggert
2022-11-15 23:43 ` Ben Boeckel
2022-11-16 14:26 ` Michael Matz
2022-11-16 14:40 ` Alexander Monakov
2022-11-16 15:01 ` Michael Matz
2022-11-16 15:27 ` Richard Biener [this message]
2022-11-16 15:35 ` Sam James
2022-11-16 15:59 ` Michael Matz
2022-11-16 16:20 ` Jonathan Wakely
2022-11-16 16:34 ` Michael Matz
2022-11-16 16:46 ` Jonathan Wakely
2022-11-16 18:17 ` Paul Eggert
2022-11-16 18:40 ` Jeffrey Walton
2022-11-17 18:45 ` Paul Eggert
2022-11-16 18:59 ` Zack Weinberg
2022-11-17 18:58 ` Paul Eggert
2022-11-17 21:35 ` Bruno Haible
2022-11-17 22:27 ` Paul Eggert
2022-11-17 13:30 ` Michael Matz
2022-11-15 20:36 ` Aaron Ballman
2022-11-15 5:03 ` Sam James
2022-11-15 13:30 ` Zack Weinberg
2022-11-15 13:34 ` Sam James
2022-11-16 0:08 ` Bob Friesenhahn
2022-11-13 0:43 ` Paul Eggert
2022-11-17 13:57 ` Jason Merrill
2022-11-10 20:19 ` Paul Eggert
[not found] ` <d785b19371e8419f5a5817d7cdb429db91614a3a.camel@orlitzky.com>
2022-11-11 3:08 ` Sam James
2022-11-11 3:33 ` Zack Weinberg
2022-11-11 8:40 ` Sam James
2022-11-11 9:02 ` Paul Eggert
2022-11-12 14:09 ` Zack Weinberg
2022-11-11 23:25 ` Sam James
2022-11-12 0:53 ` Paul Eggert
2022-11-12 4:00 ` Sam James
2022-11-11 9:15 ` Sam James
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