linux-kernel - Re: [PATCH] vsprintf: reduce code size, clean up

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Date:	Mon, 2 Nov 2009 00:18:58 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	André Goddard Rosa <andre.goddard@...il.com>
Cc:	laijs@...fujitsu.com, mingo@...e.hu, davem@...emloft.net,
	akpm@...ux-foundation.org, harvey.harrison@...il.com,
	linux list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] vsprintf: reduce code size, clean up

On Sun, Nov 01, 2009 at 09:00:48PM -0200, André Goddard Rosa wrote:
> Hi, Frederic!
> 
> On Sun, Nov 1, 2009 at 8:45 PM, Frederic Weisbecker <fweisbec@...il.com> wrote:
> > On Sun, Nov 01, 2009 at 03:01:40PM -0200, André Goddard Rosa wrote:
> >> +static char null[] = "(null)";
> >> +
> >
> >
> > This should be static const.
> > Also, may be chose a better name, as "null" is too much
> > generic and somehow collide with NULL.
> >
> > null_str ?
> >
> 
> If I make it a "static const" it's necessary to cast it in two places
> to "char *" and code size goes up
> 
> lib/vsprintf.c: In function ‘string’:
> lib/vsprintf.c:556: warning: assignment discards qualifiers from
> pointer target type
> lib/vsprintf.c: In function ‘pointer’:
> lib/vsprintf.c:828: warning: passing argument 3 of ‘string’ discards
> qualifiers from pointer target type
> lib/vsprintf.c:551: note: expected ‘char *’ but argument is of type
> ‘const char *’
> 
>    text    data     bss     dec     hex filename
>  15383       7       8   15398    3c26 lib/vsprintf.o-static-before
>  15431       0       8   15439    3c4f lib/vsprintf.o-static-const-after
> 
> as it moves the variable from data section to code section. Is this
> the preferred method?
> 


Hm, that:

static const char *null = "(null)";

is supposed to go to .rodata

Anyway, yeah better make it a const. When it's used, the variable
is not changed.

save_str in vbin_printf() is already a const char.
The "s" parameter in string() can be safely turned into const.

 
> Thanks for reviewing! I'll fix the other points per your suggestions
> and post back.
> 
> With regards,
> André


Thanks.

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