"eliminate warn_on_slowpath()" change causes many gcc-3.2.3 warnings

From: Mikael Pettersson
Date: Sat Jan 17 2009 - 10:19:54 EST

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.)

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