NodeJS源码阅读笔记

NodeJS的执行入口为：src/node_main.cc，其源码为：

#include "node.h"

#ifdef _WIN32
int wmain(int argc, wchar_t *wargv[]) {
  // Convert argv to to UTF8
  char** argv = new char*[argc];
  for (int i = 0; i < argc; i++) {
    // Compute the size of the required buffer
    DWORD size = WideCharToMultiByte(CP_UTF8,
                                     0,
                                     wargv[i],
                                     -1,
                                     nullptr,
                                     0,
                                     nullptr,
                                     nullptr);
    if (size == 0) {
      // This should never happen.
      fprintf(stderr, "Could not convert arguments to utf8.");
      exit(1);
    }
    // Do the actual conversion
    argv[i] = new char[size];
    DWORD result = WideCharToMultiByte(CP_UTF8,
                                       0,
                                       wargv[i],
                                       -1,
                                       argv[i],
                                       size,
                                       nullptr,
                                       nullptr);
    if (result == 0) {
      // This should never happen.
      fprintf(stderr, "Could not convert arguments to utf8.");
      exit(1);
    }
  }
  // Now that conversion is done, we can finally start.
  return node::Start(argc, argv);
}
#else
// UNIX
int main(int argc, char *argv[]) {
  setvbuf(stderr, NULL, _IOLBF, 1024);
  return node::Start(argc, argv);
}
#endif

其调用的node::Start方法的实现见文件src/node.cc中：

int Start(int argc, char** argv) {
  // 
  PlatformInit();

  // #define CHECK_GT(a, b) CHECK((a) > (b))
  CHECK_GT(argc, 0);

  // Hack around with the argv pointer. Used for process.title = "blah".
  // 见 deps/uv/src/unix/proctitle.c 文件中
  argv = uv_setup_args(argc, argv);

  // This needs to run *before* V8::Initialize().  The const_cast is not
  // optional, in case you're wondering.
  int exec_argc;
  const char** exec_argv;
  // 
  Init(&argc, const_cast<const char**>(argv), &exec_argc, &exec_argv);

#if HAVE_OPENSSL
  // V8 on Windows doesn't have a good source of entropy. Seed it from
  // OpenSSL's pool.
  V8::SetEntropySource(crypto::EntropySource);
#endif

  const int thread_pool_size = 4;
  default_platform = v8::platform::CreateDefaultPlatform(thread_pool_size);
  V8::InitializePlatform(default_platform);
  V8::Initialize();

  int exit_code = 1;
  {
    NodeInstanceData instance_data(NodeInstanceType::MAIN,
                                   uv_default_loop(),
                                   argc,
                                   const_cast<const char**>(argv),
                                   exec_argc,
                                   exec_argv,
                                   use_debug_agent);
    StartNodeInstance(&instance_data);
    exit_code = instance_data.exit_code();
  }
  V8::Dispose();

  delete default_platform;
  default_platform = nullptr;

  delete[] exec_argv;
  exec_argv = nullptr;

  return exit_code;
}

其中 PlatformInit() 的实现如下：

inline void PlatformInit() {
#ifdef __POSIX__
  sigset_t sigmask;
  sigemptyset(&sigmask);
  sigaddset(&sigmask, SIGUSR1);
  const int err = pthread_sigmask(SIG_SETMASK, &sigmask, nullptr);

  // Make sure file descriptors 0-2 are valid before we start logging anything.
  for (int fd = STDIN_FILENO; fd <= STDERR_FILENO; fd += 1) {
    struct stat ignored;
    if (fstat(fd, &ignored) == 0)
      continue;
    // Anything but EBADF means something is seriously wrong.  We don't
    // have to special-case EINTR, fstat() is not interruptible.
    if (errno != EBADF)
      ABORT();
    if (fd != open("/dev/null", O_RDWR))
      ABORT();
  }

  CHECK_EQ(err, 0);

  // Restore signal dispositions, the parent process may have changed them.
  struct sigaction act;
  memset(&act, 0, sizeof(act));

  // The hard-coded upper limit is because NSIG is not very reliable; on Linux,
  // it evaluates to 32, 34 or 64, depending on whether RT signals are enabled.
  // Counting up to SIGRTMIN doesn't work for the same reason.
  for (unsigned nr = 1; nr < 32; nr += 1) {
    if (nr == SIGKILL || nr == SIGSTOP)
      continue;
    act.sa_handler = (nr == SIGPIPE) ? SIG_IGN : SIG_DFL;
    CHECK_EQ(0, sigaction(nr, &act, nullptr));
  }

  RegisterSignalHandler(SIGINT, SignalExit, true);
  RegisterSignalHandler(SIGTERM, SignalExit, true);

  // Raise the open file descriptor limit.
  struct rlimit lim;
  if (getrlimit(RLIMIT_NOFILE, &lim) == 0 && lim.rlim_cur != lim.rlim_max) {
    // Do a binary search for the limit.
    rlim_t min = lim.rlim_cur;
    rlim_t max = 1 << 20;
    // But if there's a defined upper bound, don't search, just set it.
    if (lim.rlim_max != RLIM_INFINITY) {
      min = lim.rlim_max;
      max = lim.rlim_max;
    }
    do {
      lim.rlim_cur = min + (max - min) / 2;
      if (setrlimit(RLIMIT_NOFILE, &lim)) {
        max = lim.rlim_cur;
      } else {
        min = lim.rlim_cur;
      }
    } while (min + 1 < max);
  }
#endif  // __POSIX__
}