From: Michael Matz <matz@suse.de>
To: Paul Eggert <eggert@cs.ucla.edu>
Cc: 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: Thu, 17 Nov 2022 13:30:26 +0000 (UTC) [thread overview]
Message-ID: <alpine.LSU.2.20.2211171322320.5466@wotan.suse.de> (raw)
In-Reply-To: <4cfa16b3-e9e0-0ec0-659c-e4aef6090995@cs.ucla.edu>
Hello,
On Wed, 16 Nov 2022, Paul Eggert wrote:
> On 2022-11-16 06:26, Michael Matz wrote:
> > char foobar(void);
> > int main(void) {
> > return &foobar != 0;
> > }
>
> That still has undefined behavior according to draft C23,
This is correct (and also holds for the actually working variant later,
with a volatile variable). If your argument is then that as both
solutions for the link-test problem are relying on undefined behaviour
they are equivalent and hence no change is needed, you have a point, but I
disagree. In practice one (with the call) will cause more problems than
the other (with address taking).
> If Clang's threatened pickiness were of some real use elsewhere, it
> might be justifiable for default Clang to break Autoconf. But so far we
> haven't seen real-world uses that would justify this pickiness for
> Autoconf's use of 'char memset_explicit(void);'.
Note that both, GCC and clang, already warn (not error out!) about the
mismatching decl, even without any headers. So we are in the pickiness
era already.
I.e. a C file containing just a single line "char printf(void);" will be
warned about, by default. There is about nothing that autoconf could do
to rectify this, except containing a long list of prototypes for
well-known functions, with the associated maintenance hassle. But
autoconf _can_ do something about how the decls are used in the
link-tests.
Ciao,
Michael.
next prev parent reply other threads:[~2022-11-17 13:30 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
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 [this message]
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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