[libc][NFC] Move ExecuteFunction test util to test/UnitTest.

Reviewed By: lntue

Differential Revision: https://reviews.llvm.org/D148611

libc/test/UnitTest/ExecuteFunctionUnix.cpp

@@ -0,0 +1,81 @@
+//===-- ExecuteFunction implementation for Unix-like Systems --------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "ExecuteFunction.h"
+#include <cassert>
+#include <cstdlib>
+#include <cstring>
+#include <iostream>
+#include <memory>
+#include <poll.h>
+#include <signal.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+namespace __llvm_libc {
+namespace testutils {
+
+bool ProcessStatus::exited_normally() { return WIFEXITED(platform_defined); }
+
+int ProcessStatus::get_exit_code() {
+  assert(exited_normally() && "Abnormal termination, no exit code");
+  return WEXITSTATUS(platform_defined);
+}
+
+int ProcessStatus::get_fatal_signal() {
+  if (exited_normally())
+    return 0;
+  return WTERMSIG(platform_defined);
+}
+
+ProcessStatus invoke_in_subprocess(FunctionCaller *func, unsigned timeout_ms) {
+  std::unique_ptr<FunctionCaller> X(func);
+  int pipe_fds[2];
+  if (::pipe(pipe_fds) == -1)
+    return ProcessStatus::error("pipe(2) failed");
+
+  // Don't copy the buffers into the child process and print twice.
+  std::cout.flush();
+  std::cerr.flush();
+  pid_t pid = ::fork();
+  if (pid == -1)
+    return ProcessStatus::error("fork(2) failed");
+
+  if (!pid) {
+    (*func)();
+    std::exit(0);
+  }
+  ::close(pipe_fds[1]);
+
+  struct pollfd poll_fd {
+    pipe_fds[0], 0, 0
+  };
+  // No events requested so this call will only return after the timeout or if
+  // the pipes peer was closed, signaling the process exited.
+  if (::poll(&poll_fd, 1, timeout_ms) == -1)
+    return ProcessStatus::error("poll(2) failed");
+  // If the pipe wasn't closed by the child yet then timeout has expired.
+  if (!(poll_fd.revents & POLLHUP)) {
+    ::kill(pid, SIGKILL);
+    return ProcessStatus::timed_out_ps();
+  }
+
+  int wstatus = 0;
+  // Wait on the pid of the subprocess here so it gets collected by the system
+  // and doesn't turn into a zombie.
+  pid_t status = ::waitpid(pid, &wstatus, 0);
+  if (status == -1)
+    return ProcessStatus::error("waitpid(2) failed");
+  assert(status == pid);
+  return {wstatus};
+}
+
+const char *signal_as_string(int signum) { return ::strsignal(signum); }
+
+} // namespace testutils
+} // namespace __llvm_libc