src: store fd for libuv streams on Windows

On Windows, we can't just look up a FD for libuv streams and
return it in `GetFD()`.
However, we do sometimes construct streams from their FDs;
in those cases, it should be okay to store the value on a class field.

PR-URL: #19377
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: James M Snell <jasnell@gmail.com>

src/pipe_wrap.cc

@@ -204,6 +204,7 @@ void PipeWrap::Open(const FunctionCallbackInfo<Value>& args) {
   int fd = args[0]->Int32Value();
 
   int err = uv_pipe_open(&wrap->handle_, fd);
+  wrap->set_fd(fd);
 
   if (err != 0)
     env->isolate()->ThrowException(UVException(err, "uv_pipe_open"));

src/stream_wrap.cc

@@ -115,12 +115,14 @@ void LibuvStreamWrap::AddMethods(Environment* env,
 
 
 int LibuvStreamWrap::GetFD() {
+#ifdef _WIN32
+  return fd_;
+#else
   int fd = -1;
-#if !defined(_WIN32)
   if (stream() != nullptr)
     uv_fileno(reinterpret_cast<uv_handle_t*>(stream()), &fd);
-#endif
   return fd;
+#endif
 }
 
 

src/stream_wrap.h

@@ -88,6 +88,14 @@ class LibuvStreamWrap : public HandleWrap, public StreamBase {
                          v8::Local<v8::FunctionTemplate> target,
                          int flags = StreamBase::kFlagNone);
 
+ protected:
+  inline void set_fd(int fd) {
+#ifdef _WIN32
+    fd_ = fd;
+#endif
+  }
+
+
  private:
   static void GetWriteQueueSize(
       const v8::FunctionCallbackInfo<v8::Value>& info);
@@ -101,6 +109,16 @@ class LibuvStreamWrap : public HandleWrap, public StreamBase {
   static void AfterUvShutdown(uv_shutdown_t* req, int status);
 
   uv_stream_t* const stream_;
+
+#ifdef _WIN32
+  // We don't always have an FD that we could look up on the stream_
+  // object itself on Windows. However, for some cases, we open handles
+  // using FDs; In that case, we can store and provide the value.
+  // This became necessary because it allows to detect situations
+  // where multiple handles refer to the same stdio FDs (in particular,
+  // a possible IPC channel and a regular process.std??? stream).
+  int fd_ = -1;
+#endif
 };
 
 

src/tcp_wrap.cc

@@ -212,6 +212,7 @@ void TCPWrap::Open(const FunctionCallbackInfo<Value>& args) {
                           args.GetReturnValue().Set(UV_EBADF));
   int fd = static_cast<int>(args[0]->IntegerValue());
   uv_tcp_open(&wrap->handle_, fd);
+  wrap->set_fd(fd);
 }
 
 

src/tty_wrap.cc

@@ -172,6 +172,7 @@ TTYWrap::TTYWrap(Environment* env,
                       reinterpret_cast<uv_stream_t*>(&handle_),
                       AsyncWrap::PROVIDER_TTYWRAP) {
   *init_err = uv_tty_init(env->event_loop(), &handle_, fd, readable);
+  set_fd(fd);
   if (*init_err != 0)
     MarkAsUninitialized();
 }