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

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Message-ID: <YfGNRvy2KReoG/jF@smile.fi.intel.com>
Date:   Wed, 26 Jan 2022 20:04:54 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Nathan Chancellor <nathan@...nel.org>
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>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nathan Chancellor <natechancellor@...il.com>
Subject: Re: [PATCH v3 1/3] string: Make stpcpy() possible to use

On Wed, Jan 26, 2022 at 09:38:02AM -0700, Nathan Chancellor wrote:
> On Wed, Jan 26, 2022 at 04:19:15PM +0200, Andy Shevchenko wrote:
> > It is a good rule to avoid submitting code without users.
> 
> While I agree with the sentiment in the general case, I don't think that
> it applies in this case and this comment should be dropped. The message
> of the commit this fixes and the comment right above the declaration
> both make it pretty obvious why this interface was added with no in-tree
> users and why the declaration was placed right above the definition.

Thanks for accenting on this. Yes, I see now the reasoning and I don't
know which way is better. As a consumer of this API it shows a room for
micro-optimizations (I dunno if GCC and/or Clang able to replace the two
by stpcpy(), as done in the patch, at compile time).

That said, depending on the others' opinions let see how to proceed.

> > 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.
> > 
> > Fixes: 1e1b6d63d634 ("lib/string.c: implement stpcpy")
> > Reported-by: kernel test robot <lkp@...el.com>
> > Cc: Nick Desaulniers <ndesaulniers@...gle.com>
> > Cc: Nathan Chancellor <natechancellor@...il.com>
> > Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> 
> Regardless, the commit itself seems fine from a technical standpoint. I
> won't comment on whether or not this interface should be opened up.
> 
> Reviewed-by: Nathan Chancellor <nathan@...nel.org>

Thanks!

-- 
With Best Regards,
Andy Shevchenko