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From: Jiri Slaby <>
To: Tejun Heo <>, Christoph Hellwig <>
Cc:, Martin Liska <>,
	Josef Bacik <>, Jens Axboe <>,,
Subject: Re: [PATCH] block/blk-iocost (gcc13): cast enum members to int in prints
Date: Tue, 1 Nov 2022 06:46:56 +0100	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On 31. 10. 22, 18:57, Tejun Heo wrote:
> On Mon, Oct 31, 2022 at 05:24:28AM -0700, Christoph Hellwig wrote:
>> On Mon, Oct 31, 2022 at 12:45:20PM +0100, Jiri Slaby (SUSE) wrote:
>>> Cast the enum members to int when printing them.
>>> Alternatively, we can cast them to ulong (to silence gcc < 12) and use %lu.
>>> Alternatively, we can move VTIME_PER_SEC away from the enum.
>> Yes, either split the enum or just use a define.  But casts are a big
>> code smell and should be avoided if there is a reasonable alternative.
> enums are so much better for debugging and other instrumentation stuff. The
> only requirement for the enum types is that they're big enough to express
> all the members and we can use whatever printf format letter which matches
> the type in use. The problem here is that the compiler behavior is different
> depending on the compiler version, which kinda sucks.

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:

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).

> Do we know whether clang is gonna be changed the same way?

In C2x, Likely. In < C2x, dunno what'd be the default.

suse labs

  reply	other threads:[~2022-11-01  5:47 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 [this message]
2022-11-01 16:46       ` Tejun Heo
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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