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

@@ -1036,7 +1036,8 @@ static void monitor_serve_unix_socket(const char *path,
 static void interactive_sigint(int sig)
 {
     const char *const msg = "\nUse 'stop' command or Ctrl+D to exit\n";
-    write(2, msg, strlen(msg));
+    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);