linux-kernel - [PATCH] Use bool for boolean flag in printk

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Message-ID: <adak5174ezp.fsf@cisco.com>
Date:	Thu, 13 Aug 2009 13:48:26 -0700
From:	Roland Dreier <rdreier@...co.com>
To:	akpm@...ux-foundation.org
Cc:	linux-kernel@...r.kernel.org
Subject: [PATCH] Use bool for boolean flag in printk_once()

Using the type bool (instead of int) for the __print_once flag in the
printk_once() macro matches the intent of the code better, and allows
the compiler to generate smaller code; eg a typical callsite with gcc
4.3.3 on i386:

add/remove: 0/0 grow/shrink: 0/2 up/down: 0/-6 (-6)
function                                     old     new   delta
static.__print_once                            4       1      -3
get_cpu_vendor                               146     143      -3

Saving 6 bytes of object size per callsite by slightly improving the
readability of the source seems like a win to me.

Signed-off-by: Roland Dreier <rolandd@...co.com>
---
 include/linux/kernel.h |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index d6320a3..f828ce9 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -249,10 +249,10 @@ extern bool printk_timed_ratelimit(unsigned long *caller_jiffies,
  * Print a one-time message (analogous to WARN_ONCE() et al):
  */
 #define printk_once(x...) ({			\
-	static int __print_once = 1;		\
+	static bool __print_once = true;	\
 						\
 	if (__print_once) {			\
-		__print_once = 0;		\
+		__print_once = false;		\
 		printk(x);			\
 	}					\
 })
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