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

[Guenter Roeck]

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 <a...@arndb.de>

Reviewed-by: Guenter Roeck <li...@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;
  }

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