message: Exit when there is no more stdin input
diff: @@ -35,8 +35,10 @@ std::unique_ptr<BaseIpcMessage> MessageRegistry::ReadMessageFromStdin() {
  std::getline(std::cin, line);
  // No content; end of stdin.
  - if (line.empty())
  - return nullptr;
  + if (line.empty()) {
  + std::cerr << "stdin closed; exiting" << std::endl;
  + exit(0);
  + }
  // std::cin >> line;
  // std::cerr << "Read line " << line;
  