linux-kernel - [RFC PATCH 0/9] fix -Wempty-body build warnings

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Date:   Sat, 18 Apr 2020 11:41:02 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     linux-kernel@...r.kernel.org
Cc:     Randy Dunlap <rdunlap@...radead.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        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>,
        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@...ts.01.org,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        linux-scsi@...r.kernel.org, target-devel@...r.kernel.org,
        Zzy Wysm <zzy@...wysm.com>
Subject: [RFC PATCH 0/9] fix -Wempty-body build warnings

Hi,

When -Wextra is used, gcc emits many warnings about an empty 'if' or
'else' body, like this:

../fs/posix_acl.c: In function ‘get_acl’:
../fs/posix_acl.c:127:22: warning: suggest braces around empty body in an ‘if’ statement [-Wempty-body]
   /* fall through */ ;
                      ^

To quieten these warnings, add a new macro "do_empty()".
I originally wanted to use do_nothing(), but that's already in use.

It would sorta be nice if "fallthrough" could be coerced for this
instead of using something like do_empty().

Or should we just use "{}" in place of ";"?
This causes some odd coding style issue IMO. E.g., see this change:

original:
 	if (cmpxchg(p, ACL_NOT_CACHED, sentinel) != ACL_NOT_CACHED)
		/* fall through */ ;

with new macro:
 	if (cmpxchg(p, ACL_NOT_CACHED, sentinel) != ACL_NOT_CACHED)
		do_empty(); /* fall through */

using {}:
 	if (cmpxchg(p, ACL_NOT_CACHED, sentinel) != ACL_NOT_CACHED)
		{} /* fall through */
or
		{ /* fall through */ }
or even
 	if (cmpxchg(p, ACL_NOT_CACHED, sentinel) != ACL_NOT_CACHED) {
		/* fall through */ }
or
 	if (cmpxchg(p, ACL_NOT_CACHED, sentinel) != ACL_NOT_CACHED) {
		} /* fall through */


 drivers/base/devcoredump.c         |    5 +++--
 drivers/dax/bus.c                  |    5 +++--
 drivers/input/mouse/synaptics.c    |    3 ++-
 drivers/target/target_core_pscsi.c |    3 ++-
 drivers/usb/core/sysfs.c           |    2 +-
 fs/nfsd/nfs4state.c                |    3 ++-
 fs/posix_acl.c                     |    2 +-
 include/linux/kernel.h             |    8 ++++++++
 sound/drivers/vx/vx_core.c         |    3 ++-
 9 files changed, 24 insertions(+), 10 deletions(-)