watchdog: disarm on any exit once the watchdog is armed

src/main.c

@@ -23,7 +23,10 @@ void handle_error(int signo) {
     sprintf(msg, "Error occured (%d)! Quitting...\n", signo);
     write(STDERR_FILENO, msg, strlen(msg));
     keepRunning = 0;
-    exit(EXIT_FAILURE);
+    /* _exit(), not exit(): from a signal handler only async-signal-safe
+       calls are allowed, and skipping the atexit handlers leaves the
+       watchdog armed so a crash still ends in a reset */
+    _exit(EXIT_FAILURE);
 }
 
 void handle_exit(int signo) {

src/watchdog.c

@@ -21,6 +21,12 @@ int watchdog_start(int timeout) {
 
     ioctl(fd, WDIOC_SETTIMEOUT, &timeout);
 
+    /* Disarm on any normal exit from here on, including the error returns
+       out of main(), so a startup failure does not end in a reset.  A fatal
+       signal leaves through _exit() in handle_error() and keeps it armed.
+       watchdog_stop() is safe to call twice. */
+    atexit(watchdog_stop);
+
     HAL_INFO("watchdog", "Watchdog started!\n");
     return EXIT_SUCCESS;
 }