linux-toolchains.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Bill Wendling <morbo@google.com>
To: Segher Boessenkool <segher@kernel.crashing.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Nathan Chancellor <nathan@kernel.org>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	clang-built-linux <clang-built-linux@googlegroups.com>,
	LKML <linux-kernel@vger.kernel.org>,
	linux-toolchains@vger.kernel.org
Subject: Re: [PATCH v2 1/3] base: mark 'no_warn' as unused
Date: Tue, 27 Jul 2021 13:22:21 -0700	[thread overview]
Message-ID: <CAGG=3QVWxdYnjZshsYVwf+jVj8Mb9=44SZA64cL0g414JncWGw@mail.gmail.com> (raw)
In-Reply-To: <20210727201328.GY1583@gate.crashing.org>

On Tue, Jul 27, 2021 at 1:17 PM Segher Boessenkool
<segher@kernel.crashing.org> wrote:
>
> On Tue, Jul 27, 2021 at 07:59:24PM +0200, Greg Kroah-Hartman wrote:
> > On Tue, Jul 27, 2021 at 10:39:49AM -0700, Nick Desaulniers wrote:
> > > I think warn_unused_result should only really be used for functions
> > > where the return value should be used 100% of the time.
> >
> > I too want a shiny new pony.
> >
> > But here in the real world, sometimes you have functions that for 99% of
> > the users, you do want them to check the return value, but when you use
> > them in core code or startup code, you "know" you are safe to ignore the
> > return value.
> >
> > That is the case here.  We have other fun examples of where people have
> > tried to add error handling to code that runs at boot that have actually
> > introduced security errors and they justify it with "but you have to
> > check error values!"
> >
> > > If there are
> > > cases where it's ok to not check the return value, consider not using
> > > warn_unused_result on function declarations.
> >
> > Ok, so what do you do when you have a function like this where 99.9% of
> > the users need to check this?  Do I really need to write a wrapper
> > function just for it so that I can use it "safely" in the core code
> > instead?
> >
> > Something like:
> >
> > void do_safe_thing_and_ignore_the_world(...)
> > {
> >       __unused int error;
> >
> >       error = do_thing(...);
> > }
> >
> > Or something else to get the compiler to be quiet about error being set
> > and never used?
>
> The simplest is to write
>         if (do_thing()) {
>                 /* Nothing here, we can safely ignore the return value
>                  * here, because of X and Y and I don't know, I have no
>                  * idea actually why we can in this example.  Hopefully
>                  * in real code people do have a good reason :-)
>                  */
>         }
>
> which should work in *any* compiler, doesn't need any extension, is
> quite elegant, and encourages documenting why we ignore the return
> value here.
>
Or better still, use sysfs_create_link_nowarn() instead of
sysfs_create_link(). We'll just have to take the "__must_check"
attribute off the sysfs_create_link_nowarn() declaration.

-bw

  reply	other threads:[~2021-07-27 20:22 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20210714091747.2814370-1-morbo@google.com>
     [not found] ` <20210726201924.3202278-1-morbo@google.com>
     [not found]   ` <20210726201924.3202278-2-morbo@google.com>
     [not found]     ` <c965006c-88e1-3265-eb9c-76dc0bbcb733@kernel.org>
     [not found]       ` <YP+ZOx8BETgufxBS@kroah.com>
     [not found]         ` <CAGG=3QX68umw5Ws9_HuGkqoTNT=Q1+QB7YpSaqw3R_kPsbxwsg@mail.gmail.com>
     [not found]           ` <YP+ql3QFYnefR/Cf@kroah.com>
2021-07-27 17:39             ` [PATCH v2 1/3] base: mark 'no_warn' as unused Nick Desaulniers
2021-07-27 17:59               ` Greg Kroah-Hartman
2021-07-27 18:31                 ` Nick Desaulniers
2021-07-27 18:44                   ` Greg Kroah-Hartman
2021-07-27 19:02                     ` Nick Desaulniers
2021-07-27 19:23                 ` Bill Wendling
2021-07-27 20:13                 ` Segher Boessenkool
2021-07-27 20:22                   ` Bill Wendling [this message]
2021-07-27 20:24                     ` Bill Wendling
2021-07-27 18:32               ` Nathan Chancellor
2021-07-27 19:04                 ` Nick Desaulniers
2021-07-27 19:10                   ` Nathan Chancellor
2021-07-27 19:12                 ` Bill Wendling

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to='CAGG=3QVWxdYnjZshsYVwf+jVj8Mb9=44SZA64cL0g414JncWGw@mail.gmail.com' \
    --to=morbo@google.com \
    --cc=clang-built-linux@googlegroups.com \
    --cc=gregkh@linuxfoundation.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-toolchains@vger.kernel.org \
    --cc=nathan@kernel.org \
    --cc=ndesaulniers@google.com \
    --cc=rafael@kernel.org \
    --cc=segher@kernel.crashing.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).