From: Arnaldo Carvalho de Melo <acme@kernel.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: dsterba@suse.cz, Kent Overstreet <kent.overstreet@linux.dev>,
linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-bcachefs@vger.kernel.org
Subject: Re: [GIT PULL] bcachefs
Date: Wed, 6 Sep 2023 20:46:14 -0300 [thread overview]
Message-ID: <ZPkPRpe4T9RgM/CV@kernel.org> (raw)
In-Reply-To: <CAHk-=wh+RRhqgmpNN=WMz-4kkkcyNF0-a6NpRvxH9DjSTy9Ccg@mail.gmail.com>
Em Wed, Sep 06, 2023 at 04:34:32PM -0700, Linus Torvalds escreveu:
> On Wed, 6 Sept 2023 at 16:20, David Sterba <dsterba@suse.cz> wrote:
> > I think I've always seen an int for enums, unless it was
> > explicitly narrowed in the structure (:8) or by __packed attribute in
> > the enum definition.
> 'int' is definitely the default (and traditional) behavior.
> But exactly because enums can act very differently depending on
> compiler options (and some of those may have different defaults on
> different architectures), we should never ever have a bare 'enum' as
> part of a structure in any UAPI.
> In fact, having an enum as a bitfield is much better for that case.
> Doing a quick grep shows that sadly people haven't realized that.
> Now: using -fshort-enum can break a _lot_ of libraries exactly for
> this kind of reason, so the kernel isn't unusual, and I don't know of
> anybody who actually uses -fshort-enum. I'm mentioning -fshort-enum
> not because it's likely to be used, but mainly because it's an easy
> way to show some issues.
> You can get very similar issues by just having unusual enum values. Doing
>
> enum mynum { val = 0x80000000 };
> does something special too.
> I leave it to the reader to figure out, but as a hint it's basically
> exactly the same issue as I was trying to show with my crazy
> -fshort-enum example.
Two extra hints:
⬢[acme@toolbox perf-tools-next]$ grep KIND_ENUM64 include/uapi/linux/btf.h
BTF_KIND_ENUM64 = 19, /* Enumeration up to 64-bit values */
/* BTF_KIND_ENUM64 is followed by multiple "struct btf_enum64".
⬢[acme@toolbox perf-tools-next]$
⬢[acme@toolbox perf-tools-next]$ pahole --help |& grep enum
--skip_encoding_btf_enum64 Do not encode ENUM64s in BTF.
⬢[acme@toolbox perf-tools-next]$
:-)
- Arnaldo
next prev parent reply other threads:[~2023-09-06 23:52 UTC|newest]
Thread overview: 141+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-03 3:25 [GIT PULL] bcachefs Kent Overstreet
2023-09-05 13:24 ` Christoph Hellwig
2023-09-06 0:00 ` Kent Overstreet
2023-09-06 0:41 ` Matthew Wilcox
2023-09-06 16:10 ` Kent Overstreet
2023-09-06 17:57 ` Darrick J. Wong
2023-09-08 9:37 ` Christoph Hellwig
2023-09-06 19:36 ` Linus Torvalds
2023-09-06 20:02 ` Linus Torvalds
2023-09-06 20:20 ` Linus Torvalds
2023-09-06 21:55 ` Arnaldo Carvalho de Melo
2023-09-06 23:13 ` David Sterba
2023-09-06 23:34 ` Linus Torvalds
2023-09-06 23:46 ` Arnaldo Carvalho de Melo [this message]
2023-09-06 23:53 ` Arnaldo Carvalho de Melo
2023-09-06 23:16 ` Linus Torvalds
2023-09-10 0:53 ` Kent Overstreet
2023-09-07 20:37 ` Kent Overstreet
2023-09-07 20:51 ` Linus Torvalds
2023-09-07 23:40 ` Kent Overstreet
2023-09-08 6:29 ` Martin Steigerwald
2023-09-08 9:11 ` Joshua Ashton
2023-09-06 22:28 ` Nathan Chancellor
2023-09-07 0:03 ` Kees Cook
2023-09-07 14:29 ` Chris Mason
2023-09-07 20:39 ` Kent Overstreet
2023-09-08 10:50 ` Brian Foster
2023-09-08 23:05 ` Dave Chinner
2023-09-08 10:59 ` Thank you! (was: Re: [GIT PULL] bcachefs) Martin Steigerwald
-- strict thread matches above, loose matches on Subject: below --
2023-06-26 21:46 [GIT PULL] bcachefs Kent Overstreet
2023-06-26 23:11 ` Jens Axboe
2023-06-27 0:06 ` Kent Overstreet
2023-06-27 1:13 ` Jens Axboe
2023-06-27 2:05 ` Kent Overstreet
2023-06-27 2:59 ` Jens Axboe
2023-06-27 3:10 ` Kent Overstreet
2023-06-27 17:16 ` Jens Axboe
2023-06-27 20:15 ` Kent Overstreet
2023-06-27 22:05 ` Dave Chinner
2023-06-27 22:41 ` Kent Overstreet
2023-06-28 14:40 ` Jens Axboe
2023-06-28 14:48 ` Thomas Weißschuh
2023-06-28 14:58 ` Jens Axboe
2023-06-28 3:16 ` Jens Axboe
2023-06-28 4:01 ` Kent Overstreet
2023-06-28 14:58 ` Jens Axboe
2023-06-28 15:22 ` Jens Axboe
2023-06-28 17:56 ` Kent Overstreet
2023-06-28 20:45 ` Jens Axboe
2023-06-28 16:57 ` Jens Axboe
2023-06-28 17:33 ` Christian Brauner
2023-06-28 17:52 ` Kent Overstreet
2023-06-28 20:44 ` Jens Axboe
2023-06-28 21:17 ` Jens Axboe
2023-06-28 22:13 ` Kent Overstreet
2023-06-28 22:33 ` Jens Axboe
2023-06-28 22:55 ` Kent Overstreet
2023-06-28 23:14 ` Jens Axboe
2023-06-28 23:50 ` Kent Overstreet
2023-06-29 1:00 ` Dave Chinner
2023-06-29 1:33 ` Jens Axboe
2023-06-29 11:18 ` Christian Brauner
2023-06-29 14:17 ` Kent Overstreet
2023-06-29 15:31 ` Kent Overstreet
2023-06-30 9:40 ` Christian Brauner
2023-07-06 15:20 ` Kent Overstreet
2023-07-06 16:26 ` Jens Axboe
2023-07-06 16:34 ` Kent Overstreet
2023-06-29 1:29 ` Jens Axboe
2023-07-06 20:15 ` Kent Overstreet
2023-06-28 17:54 ` Kent Overstreet
2023-06-28 20:54 ` Jens Axboe
2023-06-28 22:14 ` Jens Axboe
2023-06-28 23:04 ` Kent Overstreet
2023-06-28 23:11 ` Jens Axboe
2023-06-27 2:33 ` Kent Overstreet
2023-06-27 2:59 ` Jens Axboe
2023-06-27 3:19 ` Matthew Wilcox
2023-06-27 3:22 ` Kent Overstreet
2023-06-27 3:52 ` Christoph Hellwig
2023-06-27 4:36 ` Kent Overstreet
2023-07-06 15:56 ` Kent Overstreet
2023-07-06 16:40 ` Josef Bacik
2023-07-06 17:38 ` Kent Overstreet
2023-07-06 19:17 ` Eric Sandeen
2023-07-06 19:31 ` Kent Overstreet
2023-07-06 21:19 ` Darrick J. Wong
2023-07-06 22:43 ` Kent Overstreet
2023-07-07 13:13 ` Jan Kara
2023-07-07 13:52 ` Kent Overstreet
2023-07-07 8:48 ` Christian Brauner
2023-07-07 9:18 ` Kent Overstreet
2023-07-07 16:26 ` James Bottomley
2023-07-07 16:48 ` Kent Overstreet
2023-07-07 17:04 ` James Bottomley
2023-07-07 17:26 ` Kent Overstreet
2023-07-08 3:54 ` Matthew Wilcox
2023-07-08 4:10 ` Kent Overstreet
2023-07-08 4:31 ` Kent Overstreet
2023-07-08 15:02 ` Theodore Ts'o
2023-07-08 15:23 ` Kent Overstreet
2023-07-08 16:42 ` James Bottomley
2023-07-09 1:16 ` Kent Overstreet
2023-07-07 9:35 ` Kent Overstreet
2023-07-07 2:04 ` Theodore Ts'o
2023-07-07 12:18 ` Brian Foster
2023-07-07 14:49 ` Kent Overstreet
2023-07-12 2:54 ` Kent Overstreet
2023-07-12 19:48 ` Kees Cook
2023-07-12 19:57 ` Kent Overstreet
2023-07-12 22:10 ` Darrick J. Wong
2023-07-12 23:57 ` Kent Overstreet
2023-08-09 1:27 ` Linus Torvalds
2023-08-10 15:54 ` Kent Overstreet
2023-08-10 16:40 ` Linus Torvalds
2023-08-10 18:02 ` Kent Overstreet
2023-08-10 18:09 ` Linus Torvalds
2023-08-10 17:52 ` Jan Kara
2023-08-11 2:47 ` Kent Overstreet
2023-08-11 8:10 ` Jan Kara
2023-08-11 8:13 ` Christian Brauner
2023-08-10 22:39 ` Darrick J. Wong
2023-08-10 23:47 ` Linus Torvalds
2023-08-11 2:40 ` Jens Axboe
2023-08-11 4:03 ` Kent Overstreet
2023-08-11 5:20 ` Linus Torvalds
2023-08-11 5:29 ` Kent Overstreet
2023-08-11 5:53 ` Linus Torvalds
2023-08-11 7:52 ` Christian Brauner
2023-08-11 14:31 ` Jens Axboe
2023-08-11 3:45 ` Kent Overstreet
2023-08-21 0:09 ` Dave Chinner
2023-08-10 23:07 ` Matthew Wilcox
2023-08-11 10:54 ` Christian Brauner
2023-08-11 12:58 ` Kent Overstreet
2023-08-14 7:25 ` Christian Brauner
2023-08-14 15:23 ` Kent Overstreet
2023-08-11 13:21 ` Kent Overstreet
2023-08-11 22:56 ` Darrick J. Wong
2023-08-14 7:21 ` Christian Brauner
2023-08-14 15:27 ` Kent Overstreet
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