Eliminate thousands of warnings with gcc 3.2 build

When building with gcc 3.2 I get thousands of warnings such as

include/linux/gfp.h: In function `allocflags_to_migratetype':
include/linux/gfp.h:105: warning: null format string

due to passing a NULL format string to warn_slowpath() in

#define __WARN()		warn_slowpath(__FILE__, __LINE__, NULL)

Split this case out into a separate call.  This also shrinks the kernel
slightly:

          text    data     bss     dec     hex filename
       4802274  707668  712704 6222646  5ef336 vmlinux
          text    data     bss     dec     hex filename
       4799027  703572  712704 6215303  5ed687 vmlinux

due to removeing one argument from the commonly-called __WARN().

[akpm@linux-foundation.org: reduce scope of `empty']
Acked-by: NJesper Nilsson <jesper.nilsson@axis.com>
Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
Acked-by: NArjan van de Ven <arjan@linux.intel.com>
Signed-off-by: NAndi Kleen <ak@linux.intel.com>
Cc: Hugh Dickins <hugh@veritas.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

include/asm-generic/bug.h

@@ -58,12 +58,13 @@ struct bug_entry {
  */
 #ifndef __WARN
 #ifndef __ASSEMBLY__
-extern void warn_slowpath(const char *file, const int line,
+extern void warn_slowpath_fmt(const char *file, const int line,
 		const char *fmt, ...) __attribute__((format(printf, 3, 4)));
+extern void warn_slowpath_null(const char *file, const int line);
 #define WANT_WARN_ON_SLOWPATH
 #endif
-#define __WARN()		warn_slowpath(__FILE__, __LINE__, NULL)
-#define __WARN_printf(arg...)	warn_slowpath(__FILE__, __LINE__, arg)
+#define __WARN()		warn_slowpath_null(__FILE__, __LINE__)
+#define __WARN_printf(arg...)	warn_slowpath_fmt(__FILE__, __LINE__, arg)
 #else
 #define __WARN_printf(arg...)	do { printk(arg); __WARN(); } while (0)
 #endif

kernel/panic.c

@@ -340,7 +340,7 @@ void oops_exit(void)
 }
 
 #ifdef WANT_WARN_ON_SLOWPATH
-void warn_slowpath(const char *file, int line, const char *fmt, ...)
+void warn_slowpath_fmt(const char *file, int line, const char *fmt, ...)
 {
 	va_list args;
 	char function[KSYM_SYMBOL_LEN];
@@ -356,7 +356,7 @@ void warn_slowpath(const char *file, int line, const char *fmt, ...)
 	if (board)
 		printk(KERN_WARNING "Hardware name: %s\n", board);
 
-	if (fmt) {
+	if (*fmt) {
 		va_start(args, fmt);
 		vprintk(fmt, args);
 		va_end(args);
@@ -367,7 +367,14 @@ void warn_slowpath(const char *file, int line, const char *fmt, ...)
 	print_oops_end_marker();
 	add_taint(TAINT_WARN);
 }
-EXPORT_SYMBOL(warn_slowpath);
+EXPORT_SYMBOL(warn_slowpath_fmt);
+
+void warn_slowpath_null(const char *file, int line)
+{
+	static const char *empty = "";
+	warn_slowpath_fmt(file, line, empty);
+}
+EXPORT_SYMBOL(warn_slowpath_null);
 #endif
 
 #ifdef CONFIG_CC_STACKPROTECTOR