sdk/lib/fdio/get_client.h

// Copyright 2022 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef LIB_FDIO_GET_CLIENT_H_
#define LIB_FDIO_GET_CLIENT_H_

#include <lib/fdio/directory.h>
#include <lib/fidl/cpp/wire/channel.h>
#include <lib/zx/result.h>

#include <fbl/no_destructor.h>

template <class T>
zx::result<typename fidl::WireSyncClient<T>>& get_client() {
  // We can't destroy |client| at static destruction time as some multithreaded programs call exit()
  // from one thread while other threads are calling in to fdio functions either directly or
  // indirectly through libc. Destroying |client| in this scenario would result in crashes on those
  // threads. See https://fxbug.dev/42069066 for details.
  static fbl::NoDestructor<zx::result<typename fidl::WireSyncClient<T>>> client =
      fbl::NoDestructor([]() -> zx::result<typename fidl::WireSyncClient<T>> {
        auto endpoints = fidl::CreateEndpoints<T>();
        if (endpoints.is_error()) {
          return endpoints.take_error();
        }
        zx_status_t status = fdio_service_connect_by_name(fidl::DiscoverableProtocolName<T>,
                                                          endpoints->server.channel().release());
        if (status != ZX_OK) {
          return zx::error(status);
        }
        return zx::ok(fidl::WireSyncClient(std::move(endpoints->client)));
      }());

  return *client;
}

#endif  // LIB_FDIO_GET_CLIENT_H_