linux-kernel - [PATCH] [v2] led-class-flash: fix -Wrestrict warning

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Date:   Mon, 27 Sep 2021 15:15:47 +0200
From:   Arnd Bergmann <arnd@...nel.org>
To:     Pavel Machek <pavel@....cz>
Cc:     Arnd Bergmann <arnd@...db.de>, linux-leds@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] [v2] led-class-flash: fix -Wrestrict warning

From: Arnd Bergmann <arnd@...db.de>

gcc-11 warns when building with W=1:

drivers/leds/led-class-flash.c: In function 'flash_fault_show':
drivers/leds/led-class-flash.c:210:16: error: 'sprintf' argument 3 overlaps destination object 'buf' [-Werror=restrict]
  210 |         return sprintf(buf, "%s\n", buf);
      |                ^~~~~~~~~~~~~~~~~~~~~~~~~
drivers/leds/led-class-flash.c:187:54: note: destination object referenced by 'restrict'-qualified argument 1 was declared here
  187 |                 struct device_attribute *attr, char *buf)
      |                                                ~~~~~~^~~

There is no need for the sprintf() here when a strcat() does
the same thing without invoking undefined behavior.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 drivers/leds/led-class-flash.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/leds/led-class-flash.c b/drivers/leds/led-class-flash.c
index 185e17055317..6fe9d700dfef 100644
--- a/drivers/leds/led-class-flash.c
+++ b/drivers/leds/led-class-flash.c
@@ -207,7 +207,7 @@ static ssize_t flash_fault_show(struct device *dev,
 		mask <<= 1;
 	}
 
-	return sprintf(buf, "%s\n", buf);
+	return strlen(strcat(buf, "\n"));
 }
 static DEVICE_ATTR_RO(flash_fault);
 
-- 
2.29.2