linux-kernel - Re: [PATCH v2 3/4] lib/vsprintf.c: Remove SPECIAL handling in pointer()

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Date:	Wed, 30 Sep 2015 18:40:54 +0300
From:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:	Rasmus Villemoes <linux@...musvillemoes.dk>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Tejun Heo <tj@...nel.org>, linux-kernel@...r.kernel.org,
	Kees Cook <keescook@...omium.org>,
	Joe Perches <joe@...ches.com>
Subject: Re: [PATCH v2 3/4] lib/vsprintf.c: Remove SPECIAL handling in
 pointer()

On Wed, 2015-09-30 at 17:30 +0200, Rasmus Villemoes wrote:
> As a quick
> 
>    git grep -E '%[ +0#-]*#[ +0#-]*(\*|[0-9]+)?(\.(\*|[0-9]+)?)?p'
> 
> shows, nobody uses the # flag with %p. Should one try to do so, one
> will be met with
> 
>   warning: `#' flag used with ‘%p’ gnu_printf format [-Wformat]
> 
> (POSIX and C99 both say "... For other conversion specifiers, the
> behavior is undefined.". Obviously, the kernel can choose to define
> the behaviour however it wants, but as long as gcc issues that
> warning, users are unlikely to show up.)
> 
> Since default_width is effectively always 2*sizeof(void*), we can
> simplify the prologue of pointer() and save a few instructions.
> 

Reviewed-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>

> Signed-off-by: Rasmus Villemoes <linux@...musvillemoes.dk>
> ---
> v2: reword slightly, refer to POSIX/C99.
> 
>  lib/vsprintf.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/lib/vsprintf.c b/lib/vsprintf.c
> index 03fa10b4be96..98b0d7be3fb7 100644
> --- a/lib/vsprintf.c
> +++ b/lib/vsprintf.c
> @@ -1457,7 +1457,7 @@ static noinline_for_stack
>  char *pointer(const char *fmt, char *buf, char *end, void *ptr,
>  	      struct printf_spec spec)
>  {
> -	int default_width = 2 * sizeof(void *) + (spec.flags & 
> SPECIAL ? 2 : 0);
> +	const int default_width = 2 * sizeof(void *);
>  
>  	if (!ptr && *fmt != 'K') {
>  		/*

-- 
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Intel Finland Oy
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