Adds a modified copy of talk/base to webrtc/base. It is the first step in migrating talk/base to webrtc/base.

BUG=N/A
R=andrew@webrtc.org, wu@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/12199004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@6107 4adac7df-926f-26a2-2b94-8c16560cd09d

webrtc/base/posix.cc

@@ -0,0 +1,131 @@
+/*
+ *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "webrtc/base/posix.h"
+
+#include <sys/wait.h>
+#include <errno.h>
+#include <unistd.h>
+
+#if defined(WEBRTC_LINUX) && !defined(WEBRTC_ANDROID)
+#include "webrtc/base/linuxfdwalk.h"
+#endif
+#include "webrtc/base/logging.h"
+
+namespace rtc {
+
+#if defined(WEBRTC_LINUX) && !defined(WEBRTC_ANDROID)
+static void closefds(void *close_errors, int fd) {
+  if (fd <= 2) {
+    // We leave stdin/out/err open to the browser's terminal, if any.
+    return;
+  }
+  if (close(fd) < 0) {
+    *static_cast<bool *>(close_errors) = true;
+  }
+}
+#endif
+
+enum {
+  EXIT_FLAG_CHDIR_ERRORS       = 1 << 0,
+#if defined(WEBRTC_LINUX) && !defined(WEBRTC_ANDROID)
+  EXIT_FLAG_FDWALK_ERRORS      = 1 << 1,
+  EXIT_FLAG_CLOSE_ERRORS       = 1 << 2,
+#endif
+  EXIT_FLAG_SECOND_FORK_FAILED = 1 << 3,
+};
+
+bool RunAsDaemon(const char *file, const char *const argv[]) {
+  // Fork intermediate child to daemonize.
+  pid_t pid = fork();
+  if (pid < 0) {
+    LOG_ERR(LS_ERROR) << "fork()";
+    return false;
+  } else if (!pid) {
+    // Child.
+
+    // We try to close all fds and change directory to /, but if that fails we
+    // keep going because it's not critical.
+    int exit_code = 0;
+    if (chdir("/") < 0) {
+      exit_code |= EXIT_FLAG_CHDIR_ERRORS;
+    }
+#if defined(WEBRTC_LINUX) && !defined(WEBRTC_ANDROID)
+    bool close_errors = false;
+    if (fdwalk(&closefds, &close_errors) < 0) {
+      exit_code |= EXIT_FLAG_FDWALK_ERRORS;
+    }
+    if (close_errors) {
+      exit_code |= EXIT_FLAG_CLOSE_ERRORS;
+    }
+#endif
+
+    // Fork again to become a daemon.
+    pid = fork();
+    // It is important that everything here use _exit() and not exit(), because
+    // exit() would call the destructors of all global variables in the whole
+    // process, which is both unnecessary and unsafe.
+    if (pid < 0) {
+      exit_code |= EXIT_FLAG_SECOND_FORK_FAILED;
+      _exit(exit_code);  // if second fork failed
+    } else if (!pid) {
+      // Child.
+      // Successfully daemonized. Run command.
+      // WEBRTC_POSIX requires the args to be typed as non-const for historical
+      // reasons, but it mandates that the actual implementation be const, so
+      // the cast is safe.
+      execvp(file, const_cast<char *const *>(argv));
+      _exit(255);  // if execvp failed
+    }
+
+    // Parent.
+    // Successfully spawned process, but report any problems to the parent where
+    // we can log them.
+    _exit(exit_code);
+  }
+
+  // Parent. Reap intermediate child.
+  int status;
+  pid_t child = waitpid(pid, &status, 0);
+  if (child < 0) {
+    LOG_ERR(LS_ERROR) << "Error in waitpid()";
+    return false;
+  }
+  if (child != pid) {
+    // Should never happen (see man page).
+    LOG(LS_ERROR) << "waitpid() chose wrong child???";
+    return false;
+  }
+  if (!WIFEXITED(status)) {
+    LOG(LS_ERROR) << "Intermediate child killed uncleanly";  // Probably crashed
+    return false;
+  }
+
+  int exit_code = WEXITSTATUS(status);
+  if (exit_code & EXIT_FLAG_CHDIR_ERRORS) {
+    LOG(LS_WARNING) << "Child reported probles calling chdir()";
+  }
+#if defined(WEBRTC_LINUX) && !defined(WEBRTC_ANDROID)
+  if (exit_code & EXIT_FLAG_FDWALK_ERRORS) {
+    LOG(LS_WARNING) << "Child reported problems calling fdwalk()";
+  }
+  if (exit_code & EXIT_FLAG_CLOSE_ERRORS) {
+    LOG(LS_WARNING) << "Child reported problems calling close()";
+  }
+#endif
+  if (exit_code & EXIT_FLAG_SECOND_FORK_FAILED) {
+    LOG(LS_ERROR) << "Failed to daemonize";
+    // This means the command was not launched, so failure.
+    return false;
+  }
+  return true;
+}
+
+}  // namespace rtc