file_watch: don't watch special files

While /dev/null is always empty, it still generates inotify events. So
using /dev/null as config file will cause the compositor to reset itself
frequently.

Not entire sure if only allowing regular files is sufficient, but we
will be doing this until an issue comes up.

Fixes chjj#320

Signed-off-by: Yuxuan Shui <[email protected]>

src/file_watch.c

@@ -126,6 +126,18 @@ bool file_watch_add(void *_fwr, const char *filename, file_watch_cb_t cb, void *
 	log_debug("Adding \"%s\" to watched files", filename);
 	auto fwr = (struct file_watch_registry *)_fwr;
 	int wd = -1;
+
+	struct stat statbuf;
+	int ret = stat(filename, &statbuf);
+	if (ret < 0) {
+		log_error_errno("Failed to retrieve information about file \"%s\"", filename);
+		return false;
+	}
+	if (!S_ISREG(statbuf.st_mode)) {
+		log_info("\"%s\" is not a regular file, not watching it.", filename);
+		return false;
+	}
+
 #ifdef HAS_INOTIFY
 	wd = inotify_add_watch(fwr->w.fd, filename,
 	                       IN_CLOSE_WRITE | IN_MOVE_SELF | IN_DELETE_SELF);