From: Tejun Heo <email@example.com>
To: Jiri Slaby <firstname.lastname@example.org>
Cc: Christoph Hellwig <email@example.com>,
firstname.lastname@example.org, Martin Liska <email@example.com>,
Josef Bacik <firstname.lastname@example.org>, Jens Axboe <email@example.com>,
Subject: Re: [PATCH] block/blk-iocost (gcc13): cast enum members to int in prints
Date: Tue, 1 Nov 2022 06:46:35 -1000 [thread overview]
Message-ID: <Y2FNa4bGhJoevRKT@slm.duckdns.org> (raw)
On Tue, Nov 01, 2022 at 06:46:56AM +0100, Jiri Slaby wrote:
> Yes. The real problem is that using anything else then an INT_MIN <= x <=
> INT_MAX _constant_ in an enum is undefined in ANSI C < 2x (in particular, 1
> << x is undefined too). gcc manual defines unsigned int on the top of that
> as defined too (so this holds for our -std=g*).
> > I suppose the most reasonable thing to do here is just splitting them into
> > separate enum definitions. Does anyone know how this behavior change came to
> > be?
> C2x which introduces un/signed long enums. See the bug I linked in the
> commit log:
I see. So, it was an extension but the new standard is defined differently
and we're gonna end up with that behavior.
> The change is also turned on in < C2x on purpose. AIUI, unless there is too
> much breakage. So we'd need to sort it out in (rather distant) future anyway
> (when we come up to -std=g2x).
The part that the new behavior applying to <C2x feels like an odd decision.
I'm having a hard time seeing the upsides in doing so but maybe that's just
me not knowing the area well enough.
> > Do we know whether clang is gonna be changed the same way?
> In C2x, Likely. In < C2x, dunno what'd be the default.
It looks like we can do one of the following two:
* If gcc actually changes the behavior for <c2x, split the enums according
to their sizes. This feels rather silly but I can't think of a better way
to cater to divergent compiler behaviors.
* If gcc doesn't change the behavior for <c2x, there's nothing to do for the
time being. Later when we switch to -std=g2x, we can just change the
format strings to use the now larger types.
Does the above make sense?
next prev parent reply other threads:[~2022-11-01 16:46 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-31 11:45 [PATCH] block/blk-iocost (gcc13): cast enum members to int in prints Jiri Slaby (SUSE)
2022-10-31 12:24 ` Christoph Hellwig
2022-10-31 17:57 ` Tejun Heo
2022-11-01 5:46 ` Jiri Slaby
2022-11-01 16:46 ` Tejun Heo [this message]
2022-11-02 8:35 ` David Laight
2022-11-02 16:27 ` 'Tejun Heo'
2022-11-02 16:43 ` 'Tejun Heo'
2022-12-12 12:14 ` Jiri Slaby
2022-12-12 21:46 ` 'Tejun Heo'
2022-12-13 8:30 ` David Laight
2022-12-13 11:15 ` Jiri Slaby
2022-12-13 11:50 ` David Laight
2022-12-13 12:05 ` Jiri Slaby
2022-12-13 12:58 ` David Laight
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