build: fixing unused-result warning

The results of calls to methods write() and read() are now checked in the debug build, which will help diagnose potential problems.

Signed-off-by: Aleksandr Golubev <[email protected]>

tests/vhost_user_blk_test_server.c

@@ -854,11 +854,11 @@ static int resize(struct disk *d, uint64_t new_size)
 static bool monitor_serve_fd(FILE *f_in, FILE *f_out,
                              struct disks_context *ctx)
 {
-    const char *help = "Commands:\n"
-        "  help  -  print this message\n"
-        "  stop  -  stop the server and quit\n"
-        "  stat  -  print statistics\n"
-        "  resize <new_size>  -  resize the disk\n";
+    const char *const help = "Commands:\n"
+                             "  help  -  print this message\n"
+                             "  stop  -  stop the server and quit\n"
+                             "  stat  -  print statistics\n"
+                             "  resize <new_size>  -  resize the disk\n";
 
     bool interactive = (f_in == stdin && f_out == stdout);
 
@@ -1035,8 +1035,9 @@ static void monitor_serve_unix_socket(const char *path,
 
 static void interactive_sigint(int sig)
 {
-    const char *msg = "\nUse 'stop' command or Ctrl+D to exit\n";
-    write(2, msg, strlen(msg));
+    const char *const msg = "\nUse 'stop' command or Ctrl+D to exit\n";
+    ssize_t res = write(2, msg, strlen(msg));
+    VHD_ASSERT(res == strlen(msg));
 }
 
 static void monitor_serve_stdio(struct disks_context *ctx)

vdev.c

@@ -1940,7 +1940,8 @@ static int timer_read(void *opaque)
     uint64_t count;
 
     /* Read the count to rearm the periodic timer, but ignore the result */
-    (void)read(vdev->timerfd, &count, sizeof(count));
+    ssize_t res = read(vdev->timerfd, &count, sizeof(count));
+    VHD_ASSERT(res == sizeof(count));
 
     elapsed_time(vdev, &elapsed);