From: Dan Carpenter <dan.carpenter@oracle.com>
To: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Markus Elfring <Markus.Elfring@web.de>,
kernel-janitors@vger.kernel.org,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Andrew Morton <akpm@linux-foundation.org>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Joe Perches <joe@perches.com>, Kees Cook <keescook@chromium.org>,
Nick Desaulniers <ndesaulniers@google.com>,
Steven Rostedt <rostedt@goodmis.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] string.h: Mark 34 functions with __must_check
Date: Wed, 9 Oct 2019 16:56:33 +0300 [thread overview]
Message-ID: <20191009135522.GA20194@kadam> (raw)
In-Reply-To: <954c5d70-742f-7b0e-57ad-ea967e93be89@rasmusvillemoes.dk>
[ I haven't reviewed the original patch ]
On Wed, Oct 09, 2019 at 03:26:18PM +0200, Rasmus Villemoes wrote:
> On 09/10/2019 14.14, Markus Elfring wrote:
> > From: Markus Elfring <elfring@users.sourceforge.net>
> > Date: Wed, 9 Oct 2019 13:53:59 +0200
> >
> > Several functions return values with which useful data processing
> > should be performed. These values must not be ignored then.
> > Thus use the annotation “__must_check” in the shown function declarations.
>
> This _might_ make sense for those that are basically kmalloc() wrappers
> in one way or another [1]. But what's the point of annotating pure
> functions such as strchr, strstr, memchr etc? Nobody is calling those
> for their side effects (they don't have any...), so obviously the return
> value is used. If somebody does a strcmp() without using the result, so
> what? OK, it's odd code that might be worth flagging, but I don't think
> that's the kind of thing one accidentally adds.
if (ret) {
-EINVAL;
}
People do occasionally make mistakes like this. It can't hurt to
warn them as early as possible about nonsense code.
> You're also not consistent - strlen() is not annotated. And, for the
> standard C functions, -Wall already seems to warn about an unused
> call:
>
> #include <string.h>
> int f(const char *s)
> {
> strlen(s);
> return 3;
> }
> $ gcc -Wall -o a.o -c a.c
> a.c: In function ‘f’:
> a.c:5:2: warning: statement with no effect [-Wunused-value]
> strlen(s);
> ^~~~~~~~~
That's because glibc strlen is annotated with __attribute_pure__ which
means it has no side effects.
regards,
dan carpenter
next prev parent reply other threads:[~2019-10-09 13:58 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-09 12:14 [PATCH] string.h: Mark 34 functions with __must_check Markus Elfring
2019-10-09 13:26 ` Rasmus Villemoes
2019-10-09 13:56 ` Dan Carpenter [this message]
2019-10-09 14:21 ` Rasmus Villemoes
2019-10-09 14:30 ` Dan Carpenter
2019-10-09 16:31 ` Nick Desaulniers
2019-10-09 18:45 ` Dan Carpenter
2019-10-10 7:20 ` Rasmus Villemoes
2019-10-09 16:37 ` Nick Desaulniers
2019-10-09 16:42 ` Markus Elfring
2019-10-11 5:15 ` Searching for missing variable checks Markus Elfring
2019-10-09 15:09 ` [PATCH] string.h: Mark 34 functions with __must_check Steven Rostedt
2019-10-09 16:13 ` Nick Desaulniers
2019-10-09 16:27 ` Steven Rostedt
2019-10-09 16:40 ` Nick Desaulniers
2019-10-09 17:04 ` Markus Elfring
2019-10-09 17:33 ` Nick Desaulniers
2019-10-09 18:06 ` Markus Elfring
2019-10-09 16:38 ` [PATCH] " Joe Perches
2019-10-09 17:33 ` Nick Desaulniers
2019-10-10 14:27 ` David Sterba
2019-10-10 14:34 ` Joe Perches
2019-10-11 5:00 ` Markus Elfring
2019-10-10 15:46 ` [PATCH] " David Laight
2019-10-09 20:06 ` Markus Elfring
2019-10-10 5:29 ` Andy Shevchenko
2019-10-10 7:25 ` Markus Elfring
2019-12-21 9:30 ` Markus Elfring
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