linux-kernel - Re: [PATCH v3 1/3] string: Make stpcpy() possible to use

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Message-ID: <YfGN6xOP4PTL3k3P@smile.fi.intel.com>
Date:   Wed, 26 Jan 2022 20:07:39 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     Kees Cook <keescook@...omium.org>,
        Francis Laniel <laniel_francis@...vacyrequired.com>,
        Petr Mladek <pmladek@...e.com>, linux-kernel@...r.kernel.org,
        Andy Shevchenko <andy@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        kernel test robot <lkp@...el.com>,
        Nathan Chancellor <natechancellor@...il.com>
Subject: Re: [PATCH v3 1/3] string: Make stpcpy() possible to use

On Wed, Jan 26, 2022 at 09:49:38AM -0800, Nick Desaulniers wrote:
> On Wed, Jan 26, 2022 at 6:19 AM Andy Shevchenko
> <andriy.shevchenko@...ux.intel.com> wrote:
> >
> > It is a good rule to avoid submitting code without users.
> > Currently the stpcpy() is unusable due to missed declaration.
> > Any attempts to use it will bring something like:
> >
> >   error: implicit declaration of function ‘stpcpy’ [-Werror=implicit-function-declaration]
> >
> > Move declaration to the header and guard it as other string functions.

...

> Recall the discussion from Kees:
> https://lore.kernel.org/lkml/CAK7LNAQXo5-5W6hvNMEVPBPf3tRWaf-pQdSR-0OHyi4RCGhjsQ@mail.gmail.com/
> and
> https://lore.kernel.org/lkml/202008150921.B70721A359@keescook/

> I'm guessing that the 0day bot report was on the third patch in this
> series, which looks to use stpcpy:
> https://lore.kernel.org/lkml/20220126141917.75399-3-andriy.shevchenko@linux.intel.com/
> 
> for patch 3,

Yes. It was Rasmus' suggestion.

> I'd s/"compress"/de-duplicate/ or s/"compress"/merge/.

I'll fix it locally.

> Kees, I'm curious if we can do something like require the string
> length to be known at compile time otherwise BUILD_BUG_ON?

Perhaps static_assert() is better.

-- 
With Best Regards,
Andy Shevchenko