基于Yocto交叉编译gRPC的步骤简介

版本适配：gRPC=v1.21.0, Protobuf=v3.5.0

交叉编译之前，请先编译安装本地版本的gRPC和Protobuf，注意版本适配。

第一步：初始化Yocto的交叉编译环境

source Yocto 的环境变量 environment-setup-cortexa9hf-vfp-neon-poky-linux-gnueabi

第二步：编译安装Protobuf

cd third_party/protobuf/
git submodule update --init --recursive #修改本地源方法如前文，更新第三方源码
./autogen.sh
./configure --prefix=/usr --host=arm-poky-linux-gnueabi --with-protoc=/usr/local/bin/protoc
make -j2
make DESTDIR=~/rootfs install

注意：其中DESTDIR指定交叉编译环境的安装目录，而不是本地系统环境。

第三步：配置gRPC的环境变量

注意：先修改Makefile文件，后面还需要再修改一次
prefix ?= /usr

export GRPC_CROSS_COMPILE=true
export LDXX=$CXX
export LD=$CXX
export PROTOBUF_CONFIG_OPTS="--host=arm-poky-linux-gnueabi --with-protoc=/usr/local/bin/protoc"
export GRPC_CROSS_LDOPTS=$LDFLAGS
export GRPC_CROSS_AROPTS=rc
export USE_BUILT_PROTOC=true

第四步：执行make命令并解决一些问题

问题1：src/compiler/ruby_generator.cc和src/cpp/server/channelz/channelz_service.cc依赖了Protobuf 3.6.0的头文件

解决1：替换源文件为旧版本，内容较多放在文章最后面。

问题2：

[GRPC]    Generating gRPC's protobuf service CC file from src/proto/grpc/channelz/channelz.proto
/home/help/RPC/grpc/bins/opt/grpc_cpp_plugin: program not found or is not executable
--grpc_out: protoc-gen-grpc: Plugin failed with status code 1.
Makefile:2590: recipe for target '/home/help/RPC/grpc/gens/src/proto/grpc/channelz/channelz.grpc.pb.cc' failed
make: *** [/home/help/RPC/grpc/gens/src/proto/grpc/channelz/channelz.grpc.pb.cc] Error 1

解决2：修改Makefile文件，找到变量PROTOC_PLUGINS_DIR ，覆盖所有变量赋值：PROTOC_PLUGINS_DIR = /usr/local/bin

问题3：如何交叉编译的安装？

解决3：修改Makefile文件，设置变量为： prefix ?= ~/rootfs

第五步：执行make install安装

以上，已经安装完成。

附件：

src/compiler/ruby_generator.cc

/*
 *
 * Copyright 2015 gRPC authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */

#include 
#include 

src/cpp/server/channelz/channelz_service.cc

/*
 *
 * Copyright 2018 gRPC authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */

#include 

#include "src/cpp/server/channelz/channelz_service.h"

#include 
#include 

namespace grpc {

Status ChannelzService::GetTopChannels(
    ServerContext* unused, const channelz::v1::GetTopChannelsRequest* request,
    channelz::v1::GetTopChannelsResponse* response) {
  char* json_str = grpc_channelz_get_top_channels(request->start_channel_id());
  if (json_str == nullptr) {
    return Status(StatusCode::INTERNAL,
                  "grpc_channelz_get_top_channels returned null");
  }
  grpc::protobuf::util::Status s =
      grpc::protobuf::json::JsonStringToMessage(json_str, response);
  gpr_free(json_str);
  if (!s.ok()) {
    return Status(StatusCode::INTERNAL, s.ToString());
  }
  return Status::OK;
}

Status ChannelzService::GetServers(
    ServerContext* unused, const channelz::v1::GetServersRequest* request,
    channelz::v1::GetServersResponse* response) {
  char* json_str = grpc_channelz_get_servers(request->start_server_id());
  if (json_str == nullptr) {
    return Status(StatusCode::INTERNAL,
                  "grpc_channelz_get_servers returned null");
  }
  grpc::protobuf::util::Status s =
      grpc::protobuf::json::JsonStringToMessage(json_str, response);
  gpr_free(json_str);
  if (!s.ok()) {
    return Status(StatusCode::INTERNAL, s.ToString());
  }
  return Status::OK;
}

Status ChannelzService::GetServer(ServerContext* unused,
                                  const channelz::v1::GetServerRequest* request,
                                  channelz::v1::GetServerResponse* response) {
  char* json_str = grpc_channelz_get_server(request->server_id());
  if (json_str == nullptr) {
    return Status(StatusCode::INTERNAL,
                  "grpc_channelz_get_server returned null");
  }
  grpc::protobuf::util::Status s =
      grpc::protobuf::json::JsonStringToMessage(json_str, response);
  gpr_free(json_str);
  if (!s.ok()) {
    return Status(StatusCode::INTERNAL, s.ToString());
  }
  return Status::OK;
}

Status ChannelzService::GetServerSockets(
    ServerContext* unused, const channelz::v1::GetServerSocketsRequest* request,
    channelz::v1::GetServerSocketsResponse* response) {
  char* json_str = grpc_channelz_get_server_sockets(
      request->server_id(), request->start_socket_id(), request->max_results());
  if (json_str == nullptr) {
    return Status(StatusCode::INTERNAL,
                  "grpc_channelz_get_server_sockets returned null");
  }
  grpc::protobuf::util::Status s =
      grpc::protobuf::json::JsonStringToMessage(json_str, response);
  gpr_free(json_str);
  if (!s.ok()) {
    return Status(StatusCode::INTERNAL, s.ToString());
  }
  return Status::OK;
}

Status ChannelzService::GetChannel(
    ServerContext* unused, const channelz::v1::GetChannelRequest* request,
    channelz::v1::GetChannelResponse* response) {
  char* json_str = grpc_channelz_get_channel(request->channel_id());
  if (json_str == nullptr) {
    return Status(StatusCode::NOT_FOUND, "No object found for that ChannelId");
  }
  grpc::protobuf::util::Status s =
      grpc::protobuf::json::JsonStringToMessage(json_str, response);
  gpr_free(json_str);
  if (!s.ok()) {
    return Status(StatusCode::INTERNAL, s.ToString());
  }
  return Status::OK;
}

Status ChannelzService::GetSubchannel(
    ServerContext* unused, const channelz::v1::GetSubchannelRequest* request,
    channelz::v1::GetSubchannelResponse* response) {
  char* json_str = grpc_channelz_get_subchannel(request->subchannel_id());
  if (json_str == nullptr) {
    return Status(StatusCode::NOT_FOUND,
                  "No object found for that SubchannelId");
  }
  grpc::protobuf::util::Status s =
      grpc::protobuf::json::JsonStringToMessage(json_str, response);
  gpr_free(json_str);
  if (!s.ok()) {
    return Status(StatusCode::INTERNAL, s.ToString());
  }
  return Status::OK;
}

Status ChannelzService::GetSocket(ServerContext* unused,
                                  const channelz::v1::GetSocketRequest* request,
                                  channelz::v1::GetSocketResponse* response) {
  char* json_str = grpc_channelz_get_socket(request->socket_id());
  if (json_str == nullptr) {
    return Status(StatusCode::NOT_FOUND, "No object found for that SocketId");
  }
  grpc::protobuf::util::Status s =
      grpc::protobuf::json::JsonStringToMessage(json_str, response);
  gpr_free(json_str);
  if (!s.ok()) {
    return Status(StatusCode::INTERNAL, s.ToString());
  }
  return Status::OK;
}

}  // namespace grpc