netdev - Re: [PATCH v3] Compiler Attributes: remove CONFIG_ENABLE_MUST

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Date:   Sun, 13 Dec 2020 17:32:38 +0100
From:   Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
To:     Matthias Urlichs <matthias@...ichs.de>
Cc:     Greg KH <gregkh@...uxfoundation.org>,
        Guenter Roeck <linux@...ck-us.net>,
        Masahiro Yamada <masahiroy@...nel.org>,
        "Jason A . Donenfeld" <Jason@...c4.com>,
        Nathan Chancellor <natechancellor@...il.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Shuah Khan <shuah@...nel.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>,
        Network Development <netdev@...r.kernel.org>,
        wireguard@...ts.zx2c4.com
Subject: Re: [PATCH v3] Compiler Attributes: remove CONFIG_ENABLE_MUST_CHECK

On Sun, Dec 13, 2020 at 4:38 PM 'Matthias Urlichs' via Clang Built
Linux <clang-built-linux@...glegroups.com> wrote:
>
> If your change to a function breaks its callers, it's your job to fix

No function has changed. This patch enables a warning (that for some
reason is an error in the case of Guenter).

Even if this was a hard error, the same applies: the function hasn't
changed. It just means callers never tested with
`CONFIG_ENABLE_MUST_CHECK` for *years*.

> the callers proactively instead of waiting for "as they come" bug
> reports. (Assuming, of course, that you know about the breakage. Which
> you do when you tell us that the bad pattern can simply be grepped for.)

No, *we don't know about the breakage*. The grep was for the
particular function Guenter reported, and done to validate his
concern.

If you want to manually inspect every caller of every `__must_check`
function, or to write a cocci patch or a clang-tidy check or similar
(that would be obsolete as soon as `__must_check` is enabled), you are
welcome to do so. But a much better usage of our time would be letting
machines do their job.

> If nothing else, that's far more efficient than [number_of_callers]
> separate patches by other people who each need to find the offending
> change, figure out what to change and/or who to report the problem to,
> and so on until the fix lands in the kernel.

This change is not in Linus' tree, it is on -next.

> Moreover, this wouldn't leave the kernel sources in a non-bisect-able
> state during that time.

Again, the change is in -next. That is the point: to do integration
testing and let the bots run against it.

Cheers,
Miguel