From: Florian Weimer <fweimer@redhat.com>
To: Jakub Jelinek <jakub@redhat.com>
Cc: Jason Merrill <jason@redhat.com>, gcc@gcc.gnu.org
Subject: Re: C89 question: Do we need to accept -Wint-conversion warnings
Date: Tue, 10 Oct 2023 19:06:56 +0200 [thread overview]
Message-ID: <87y1ga8kzz.fsf@oldenburg.str.redhat.com> (raw)
In-Reply-To: <ZSV9/11+S1kl+wuU@tucnak> (Jakub Jelinek's message of "Tue, 10 Oct 2023 18:38:23 +0200")
* Jakub Jelinek:
> On Tue, Oct 10, 2023 at 12:30:52PM -0400, Jason Merrill via Gcc wrote:
>> On Tue, Oct 10, 2023 at 7:30 AM Florian Weimer via Gcc <gcc@gcc.gnu.org>
>> wrote:
>>
>> > Are these code fragments valid C89 code?
>> >
>> > int i1 = 1;
>> > char *p1 = i;
>> >
>> > char c;
>> > char *p2 = &c;
>> > int i2 = p2;
>> >
>> > Or can we generate errors for them even with -std=gnu89?
>> >
>> > (It will still be possible to override this with -fpermissive or
>> > -Wno-int-conversion.)
>> >
>>
>> Given that C89 code is unlikely to be actively maintained, I think we
>> should be permissive by default in that mode. People compiling with an old
>> -std flag are presumably doing it to keep old code compiling, and it seems
>> appropriate to respect that.
>
> Yeah, complete agreement here.
Okay. It helps with the test suite conversation because -std=gnu89 -w
is available today, so I can post such patches separately.
>> I'm also (though less strongly) inclined to be permissive in C99 mode, and
>> only introduce the new strictness by default for C11/C17 modes.
>
> Especially when the default is -std=gnu17 that can be an option as well.
>
> There might be some code in the wild compiled with -std=gnu99 or -std=c99 just
> because it wanted to use C99 features back 15-20 years ago and hasn't been
> adjusted since then, but it might be better to adjust that if needed and keep
> using those flags only when they are needed because the code isn't C11/C17/C2X
> ready.
Linux currently uses -std=gnu99 deliberately in a few places, I believe.
It would be a shame if we defaulted to permissive mode over there. I
would certainly prefer to restrict permissive mode to the C89/C90
language levels. We can have this discussion once I post my patch
(which depends on Jason's permerror enhancement in several ways).
Thanks,
Florian
next prev parent reply other threads:[~2023-10-10 17:07 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-10 11:29 Florian Weimer
2023-10-10 16:30 ` Jason Merrill
2023-10-10 16:38 ` Jakub Jelinek
2023-10-10 17:06 ` Florian Weimer [this message]
2023-10-10 17:38 ` Joel Sherrill
2023-10-11 7:36 ` David Brown
2023-10-11 8:10 ` Florian Weimer
2023-10-11 8:51 ` David Brown
2023-10-11 10:17 ` Florian Weimer
2023-10-11 11:28 ` David Brown
2023-10-11 11:38 ` Florian Weimer
2023-10-10 16:38 ` Joseph Myers
2023-10-10 17:07 ` Florian Weimer
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