linux-kernel - Re: [PATCH 2/9] fs: fix empty-body warning in posix

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Message-ID: <CAHk-=wjSzuTyyBkmMDG4fx_sXzLJsh+9Xk-ubgbpJzJq_kzPsA@mail.gmail.com>
Date:   Sat, 18 Apr 2020 11:53:03 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Randy Dunlap <rdunlap@...radead.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        linux-input@...r.kernel.org, Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>, alsa-devel@...a-project.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org,
        "J. Bruce Fields" <bfields@...ldses.org>,
        Chuck Lever <chuck.lever@...cle.com>,
        "open list:NFS, SUNRPC, AND..." <linux-nfs@...r.kernel.org>,
        Johannes Berg <johannes@...solutions.net>,
        Dan Williams <dan.j.williams@...el.com>,
        Vishal Verma <vishal.l.verma@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        linux-nvdimm <linux-nvdimm@...ts.01.org>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        linux-scsi <linux-scsi@...r.kernel.org>,
        target-devel <target-devel@...r.kernel.org>,
        Zzy Wysm <zzy@...wysm.com>
Subject: Re: [PATCH 2/9] fs: fix empty-body warning in posix_acl.c

On Sat, Apr 18, 2020 at 11:41 AM Randy Dunlap <rdunlap@...radead.org> wrote:
>
> Fix gcc empty-body warning when -Wextra is used:

Please don't do this.

First off, "do_empty()" adds nothing but confusion. Now it
syntactically looks like it does something, and it's a new pattern to
everybody. I've never seen it before.

Secondly, even if we were to do this, then the patch would be wrong:

>         if (cmpxchg(p, ACL_NOT_CACHED, sentinel) != ACL_NOT_CACHED)
> -               /* fall through */ ;
> +               do_empty(); /* fall through */

That comment made little sense before, but it makes _no_ sense now.

What fall-through? I'm guessing it meant to say "nothing", and
somebody was confused. With "do_empty()", it's even more confusing.

Thirdly, there's a *reason* why "-Wextra" isn't used.

The warnings enabled by -Wextra are usually complete garbage, and
trying to fix them often makes the code worse. Exactly like here.

             Linus