Re: [PATCH v2] Documentation/watchdog: check return value for magic close

[Guenter Roeck <linux@roeck-us.net>]

On 07/19/2016 08:41 AM, Arnd Bergmann wrote:
> A recent commit added a write to the watchdog test code for doing the "magic
> close", but that caused a compile-time warning:
>
> Documentation/watchdog/src/watchdog-test.c: In function ‘main’:
> Documentation/watchdog/src/watchdog-test.c:94:5: warning: ignoring return value of ‘write’, declared with attribute warn_unused_result [-Wunused-result]
>
> This changes the code to print a runtime warning if the write fails.
>
> Fixes: 5a2d3de19602 ("Documentation/watchdog: add support for magic close to watchdog-test")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Reviewed-by: Guenter Roeck <linux@roeck-us.net>

> ---
> v2: fix typo as pointed out by both Guenter Roeck and Randy Dunlap
> ---
>   Documentation/watchdog/src/watchdog-test.c | 14 +++++++++++---
>   1 file changed, 11 insertions(+), 3 deletions(-)
>
> diff --git a/Documentation/watchdog/src/watchdog-test.c b/Documentation/watchdog/src/watchdog-test.c
> index c69153913722..6983d05097e2 100644
> --- a/Documentation/watchdog/src/watchdog-test.c
> +++ b/Documentation/watchdog/src/watchdog-test.c
> @@ -2,6 +2,7 @@
>    * Watchdog Driver Test Program
>    */
>
> +#include <errno.h>
>   #include <stdio.h>
>   #include <stdlib.h>
>   #include <string.h>
> @@ -35,9 +36,13 @@ static void keep_alive(void)
>
>   static void term(int sig)
>   {
> -    write(fd, &v, 1);
> +    int ret = write(fd, &v, 1);
> +
>       close(fd);
> -    printf("\nStopping watchdog ticks...\n");
> +    if (ret < 0)
> +	printf("\nStopping watchdog ticks failed (%d)...\n", errno);
> +    else
> +	printf("\nStopping watchdog ticks...\n");
>       exit(0);
>   }
>
> @@ -45,6 +50,7 @@ int main(int argc, char *argv[])
>   {
>       int flags;
>       unsigned int ping_rate = 1;
> +    int ret;
>
>       setbuf(stdout, NULL);
>
> @@ -91,7 +97,9 @@ int main(int argc, char *argv[])
>   	sleep(ping_rate);
>       }
>   end:
> -    write(fd, &v, 1);
> +    ret = write(fd, &v, 1);
> +    if (ret < 0)
> +	printf("Stopping watchdog ticks failed (%d)...\n", errno);
>       close(fd);
>       return 0;
>   }
>