linux-kernel - Re: "eliminate warn_on_slowpath()" change causes many gcc-3.2.3 warnings

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Date:	Sat, 17 Jan 2009 17:18:17 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Mikael Pettersson <mikpe@...uu.se>,
	"H. Peter Anvin" <hpa@...or.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: "eliminate warn_on_slowpath()" change causes many gcc-3.2.3
	warnings


* Mikael Pettersson <mikpe@...uu.se> wrote:

> Commit ec5679e513305f1411753e5f5489935bd638af23 "eliminate warn_on_slowpath()"
> changed __WARN() to call warn_slowpath() with a NULL value for the format
> string parameter. Now every WARN_ON() triggers a warning from gcc-3.2.3:
> 
> In file included from include/linux/kmod.h:22,
>                  from include/linux/module.h:13,
>                  from include/linux/crypto.h:21,
>                  from arch/x86/kernel/asm-offsets_32.c:7,
>                  from arch/x86/kernel/asm-offsets.c:2:
> include/linux/gfp.h: In function `allocflags_to_migratetype':
> include/linux/gfp.h:104: warning: null format string
> 
> Compiling kernel 2.6.29-rc2 with a minimalistic .config for my 486
> generates 1767 'null format string' warnings.
> 
> warn_slowpath() is declared with attribute((format(printf, 3, 4))),
> and gcc-3.2.3 warns if the format string parameter is NULL. gcc-3.3
> and newer do not warn in that case.
> 
> Since gcc-3.2 is still a supported compiler for the kernel, this is
> a regression.
> 
> (Just FYI. I don't consider this serious enough to warrant reverting 
> that cleanup patch or declaring gcc-3.2.3 too old. I can always update 
> my 486 to gcc-3.3.6 if the warnings start to bug me too much.)

hm, that's unfortunate. GCC seems totally on crack for not accepting a 
NULL format string.

	Ingo
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