Function ExecDeathTestSpawnChild

test/gtest/gtest-all.cc:7496–7588

Spawns a child process with the same executable as the current process in a thread-safe manner and instructs it to run the death test. The implementation uses fork(2) + exec. On systems where clone(2) is available, it is used instead, being slightly more thread-safe. On QNX, fork supports only single-threaded environments, so this function uses spawn(2) there instead. The function dies with an

// spawn(2) there instead.  The function dies with an error message if
// anything goes wrong.
static pid_t ExecDeathTestSpawnChild(char* const* argv, int close_fd) {
  ExecDeathTestArgs args = { argv, close_fd };
  pid_t child_pid = -1;

#  if GTEST_OS_QNX
  // Obtains the current directory and sets it to be closed in the child
  // process.
  const int cwd_fd = open(".", O_RDONLY);
  GTEST_DEATH_TEST_CHECK_(cwd_fd != -1);
  GTEST_DEATH_TEST_CHECK_SYSCALL_(fcntl(cwd_fd, F_SETFD, FD_CLOEXEC));
  // We need to execute the test program in the same environment where
  // it was originally invoked.  Therefore we change to the original
  // working directory first.
  const char* const original_dir =
      UnitTest::GetInstance()->original_working_dir();
  // We can safely call chdir() as it's a direct system call.
  if (chdir(original_dir) != 0) {
    DeathTestAbort(std::string("chdir(\"") + original_dir + "\") failed: " +
                   GetLastErrnoDescription());
    return EXIT_FAILURE;
  }

  int fd_flags;
  // Set close_fd to be closed after spawn.
  GTEST_DEATH_TEST_CHECK_SYSCALL_(fd_flags = fcntl(close_fd, F_GETFD));
  GTEST_DEATH_TEST_CHECK_SYSCALL_(fcntl(close_fd, F_SETFD,
                                        fd_flags | FD_CLOEXEC));
  struct inheritance inherit = {0};
  // spawn is a system call.
  child_pid = spawn(args.argv[0], 0, NULL, &inherit, args.argv, GetEnviron());
  // Restores the current working directory.
  GTEST_DEATH_TEST_CHECK_(fchdir(cwd_fd) != -1);
  GTEST_DEATH_TEST_CHECK_SYSCALL_(close(cwd_fd));

#  else   // GTEST_OS_QNX
#   if GTEST_OS_LINUX
  // When a SIGPROF signal is received while fork() or clone() are executing,
  // the process may hang. To avoid this, we ignore SIGPROF here and re-enable
  // it after the call to fork()/clone() is complete.
  struct sigaction saved_sigprof_action;
  struct sigaction ignore_sigprof_action;
  memset(&ignore_sigprof_action, 0, sizeof(ignore_sigprof_action));
  sigemptyset(&ignore_sigprof_action.sa_mask);
  ignore_sigprof_action.sa_handler = SIG_IGN;
  GTEST_DEATH_TEST_CHECK_SYSCALL_(sigaction(
      SIGPROF, &ignore_sigprof_action, &saved_sigprof_action));
#   endif  // GTEST_OS_LINUX

#   if GTEST_HAS_CLONE
  const bool use_fork = GTEST_FLAG(death_test_use_fork);

  if (!use_fork) {
    static const bool stack_grows_down = StackGrowsDown();
    const size_t stack_size = getpagesize();
    // MMAP_ANONYMOUS is not defined on Mac, so we use MAP_ANON instead.
    void* const stack = mmap(NULL, stack_size, PROT_READ | PROT_WRITE,
                             MAP_ANON | MAP_PRIVATE, -1, 0);
    GTEST_DEATH_TEST_CHECK_(stack != MAP_FAILED);