Handle signal handler setup error properly in head process

main.c

@@ -83,7 +83,14 @@ int main(int argc, char* const* argv)
       pid_child = pid;
       if (sigaction(SIGTERM, &forward_signal_descriptor, NULL) == -1)
         {
-          printf("Unable to setup signal handler in head\n");
+          int err = errno;
+          // Have to kill child here, otherwise that gets orphaned and runs anyway.
+          // Use SIGKILL here because it might forward SIGTERM to its child and that
+          // decides not to stop.
+          kill(pid_child, SIGKILL);
+          // Restore errno as it might've been overwritten by kill
+          errno = err;
+          err(errno, "Unable to set up signal handler in head process");
         }
       // parent waits for child then exits
       // Could be interrupt due to a signal. Retry in that case.