使用cmake创建protobuf/grpc cc文件

Question

如果我想在 cmake 中重新创建以下 protoc 命令：

protoc -I ../proto/ --cpp_out=. service.proto

我在 cmake 中使用以下几行：

file(GLOB ProtoFiles "${CMAKE_CURRENT_SOURCE_DIR}/*.proto")
PROTOBUF_GENERATE_CPP(ProtoSources ProtoHeaders ${ProtoFiles})

如果我想重新创建下面的 protoc 命令：

protoc -I ../proto/ --grpc_out=. --plugin=protoc-gen-grpc=`which grpc_cpp_plugin` service.proto

在上述情况下我无法确定如何更改 cmake 文件，请帮助！

问题是我该如何解决：

--plugin=EXECUTABLE           Specifies a plugin executable to use.
                              Normally, protoc searches the PATH for
                              plugins, but you may specify additional
                              executables not in the path using this flag.
                              Additionally, EXECUTABLE may be of the form
                              NAME=PATH, in which case the given plugin name
                              is mapped to the given executable even if
                              the executable's own name differs.

我一直在阅读 PROTOBUF_GENERATE_CPP 文档，但没有找到答案！

Answer 1

对我来说，https://www.falkoaxmann.de/dev/2020/11/08/grpc-plugin-cmake-support.html 的博文会带来成功，因为它提供了一个完整的示例（感谢 @powerpete）。

我将代码放在这里，因此它可以作为答案而不仅仅是作为评论：

project(my-service VERSION 1.0 LANGUAGES CXX C)

find_package(protobuf CONFIG REQUIRED)
find_package(gRPC CONFIG REQUIRED)
find_package(Threads)

set(PROTO_FILES
    MyService.proto
)

# protobuf source files go into the lib just like any other CPP source file
add_library(my-service ${PROTO_FILES})
target_link_libraries(my-service
    PUBLIC
        protobuf::libprotobuf
        gRPC::grpc
        gRPC::grpc++
)

target_include_directories(my-service
    PUBLIC
        ${CMAKE_CURRENT_BINARY_DIR}
)

get_target_property(grpc_cpp_plugin_location gRPC::grpc_cpp_plugin LOCATION)

# compile the message types
protobuf_generate(TARGET my-service LANGUAGE cpp)

# compile the GRPC services
protobuf_generate(
    TARGET
        my-service
    LANGUAGE
        grpc
    GENERATE_EXTENSIONS
        .grpc.pb.h
        .grpc.pb.cc
    PLUGIN
        "protoc-gen-grpc=${grpc_cpp_plugin_location}"
)

Answer 2

从 3.12 版本开始，protobuf_generate 支持 PLUGIN 参数

https://github.com/protocolbuffers/protobuf/blob/v3.12.0/cmake/protobuf-config.cmake.in#L46

所以您可以尝试以下方法： PROTOBUF_GENERATE_CPP(ProtoSources ProtoHeaders ${ProtoFiles} PLUGIN protoc-gen-grpc=${GRPC_CPP_PLUGIN_PATH})

Answer 3

模块 findProtobuf.cmake 仅为常见的 protoc 调用定义函数包装器：PROTOBUF_GENERATE_CPP - 用于 --cpp_out 和 PROTOBUF_GENERATE_PYTHON - 用于 --py_out。但是您可以为所需的插件实现自己的函数包装器。下面的代码基于PROTOBUF_GENERATE_CPP 实现。

find_program(GRPC_CPP_PLUGIN grpc_cpp_plugin) # Get full path to plugin

function(PROTOBUF_GENERATE_GRPC_CPP SRCS HDRS)
  if(NOT ARGN)
    message(SEND_ERROR "Error: PROTOBUF_GENERATE_GRPC_CPP() called without any proto files")
    return()
  endif()

  if(PROTOBUF_GENERATE_CPP_APPEND_PATH) # This variable is common for all types of output.
    # Create an include path for each file specified
    foreach(FIL ${ARGN})
      get_filename_component(ABS_FIL ${FIL} ABSOLUTE)
      get_filename_component(ABS_PATH ${ABS_FIL} PATH)
      list(FIND _protobuf_include_path ${ABS_PATH} _contains_already)
      if(${_contains_already} EQUAL -1)
          list(APPEND _protobuf_include_path -I ${ABS_PATH})
      endif()
    endforeach()
  else()
    set(_protobuf_include_path -I ${CMAKE_CURRENT_SOURCE_DIR})
  endif()

  if(DEFINED PROTOBUF_IMPORT_DIRS)
    foreach(DIR ${Protobuf_IMPORT_DIRS})
      get_filename_component(ABS_PATH ${DIR} ABSOLUTE)
      list(FIND _protobuf_include_path ${ABS_PATH} _contains_already)
      if(${_contains_already} EQUAL -1)
          list(APPEND _protobuf_include_path -I ${ABS_PATH})
      endif()
    endforeach()
  endif()

  set(${SRCS})
  set(${HDRS})
  foreach(FIL ${ARGN})
    get_filename_component(ABS_FIL ${FIL} ABSOLUTE)
    get_filename_component(FIL_WE ${FIL} NAME_WE)

    list(APPEND ${SRCS} "${CMAKE_CURRENT_BINARY_DIR}/${FIL_WE}.grpc.pb.cc")
    list(APPEND ${HDRS} "${CMAKE_CURRENT_BINARY_DIR}/${FIL_WE}.grpc.pb.h")

    add_custom_command(
      OUTPUT "${CMAKE_CURRENT_BINARY_DIR}/${FIL_WE}.grpc.pb.cc"
             "${CMAKE_CURRENT_BINARY_DIR}/${FIL_WE}.grpc.pb.h"
      COMMAND  ${Protobuf_PROTOC_EXECUTABLE}
      ARGS --grpc_out=${CMAKE_CURRENT_BINARY_DIR}
           --plugin=protoc-gen-grpc=${GRPC_CPP_PLUGIN}
           ${_protobuf_include_path} ${ABS_FIL}
      DEPENDS ${ABS_FIL} ${Protobuf_PROTOC_EXECUTABLE}
      COMMENT "Running gRPC C++ protocol buffer compiler on ${FIL}"
      VERBATIM)
  endforeach()

  set_source_files_properties(${${SRCS}} ${${HDRS}} PROPERTIES GENERATED TRUE)
  set(${SRCS} ${${SRCS}} PARENT_SCOPE)
  set(${HDRS} ${${HDRS}} PARENT_SCOPE)
endfunction()

用法同PROTOBUF_GENERATE_CPP:

file(GLOB ProtoFiles "${CMAKE_CURRENT_SOURCE_DIR}/*.proto")
PROTOBUF_GENERATE_GRPC_CPP(ProtoGRPCSources ProtoGRPCHeaders ${ProtoFiles})