gRPC + flatbuffers を自前 C++ プロジェクトに取り込むときのメモ

  set(GRPC_AS_SUBMODULE On)

  if(GRPC_AS_SUBMODULE)
    # One way to build a projects that uses gRPC is to just include the entire
    # gRPC project tree via "add_subdirectory". This approach is very simple to
    # use, but the are some potential disadvantages: * it includes gRPC's
    # CMakeLists.txt directly into your build script without and that can make
    # gRPC's internal setting interfere with your own build. * depending on
    # what's installed on your system, the contents of submodules in gRPC's
    # third_party/* might need to be available (and there might be additional
    # prerequisites required to build them). Consider using the gRPC_*_PROVIDER
    # options to fine-tune the expected behavior.
    #
    # A more robust approach to add dependency on gRPC is using cmake's
    # ExternalProject_Add (see cmake_externalproject/CMakeLists.txt).

    # Include the gRPC's cmake build (normally grpc source code would live in a
    # git submodule called "third_party/grpc", but this example lives in the
    # same repository as gRPC sources, so we just look a few directories up)
    add_subdirectory(${CMAKE_SOURCE_DIR}/externals/grpc
                     ${CMAKE_CURRENT_BINARY_DIR}/grpc EXCLUDE_FROM_ALL)
    message(STATUS "Using gRPC via add_subdirectory.")

    # After using add_subdirectory, we can now use the grpc targets directly
    # from this build. set(_PROTOBUF_LIBPROTOBUF libprotobuf)
    # set(_PROTOBUF_PROTOC $<TARGET_FILE:protoc>)
    set(_GRPC_GRPCPP_UNSECURE grpc++_unsecure)
    set(_GRPC_CPP_PLUGIN_EXECUTABLE $<TARGET_FILE:grpc_cpp_plugin>)
  else()
    # This branch assumes that gRPC and all its dependencies are already
    # installed on this system, so they can be located by find_package().

    # Find Protobuf installation Looks for protobuf-config.cmake file installed
    # by Protobuf's cmake installation.
    set(protobuf_MODULE_COMPATIBLE TRUE)
    find_package(Protobuf CONFIG REQUIRED)
    message(STATUS "Using protobuf ${protobuf_VERSION}")

    set(_PROTOBUF_LIBPROTOBUF protobuf::libprotobuf)
    set(_PROTOBUF_PROTOC $<TARGET_FILE:protobuf::protoc>)

    # Find gRPC installation Looks for gRPCConfig.cmake file installed by gRPC's
    # cmake installation.
    find_package(gRPC CONFIG REQUIRED)
    message(STATUS "Using gRPC ${gRPC_VERSION}")

    set(_GRPC_GRPCPP_UNSECURE gRPC::grpc++_unsecure)
    set(_GRPC_CPP_PLUGIN_EXECUTABLE $<TARGET_FILE:gRPC::grpc_cpp_plugin>)
  endif()

  # Proto file get_filename_component(hotreload_proto
  # "${CMAKE_SOURCE_DIR}/src/hotreload/hotreload.proto" ABSOLUTE)
  # get_filename_component(hotreload_proto_path "${hotreload_proto}" PATH)

  # Generated sources set(hotreload_proto_srcs
  # "${CMAKE_CURRENT_BINARY_DIR}/hotreload.pb.cc") set(hotreload_proto_hdrs
  # "${CMAKE_CURRENT_BINARY_DIR}/hotreload.pb.h") set(hotreload_grpc_srcs
  # "${CMAKE_CURRENT_BINARY_DIR}/hotreload.grpc.pb.cc") set(hotreload_grpc_hdrs
  # "${CMAKE_CURRENT_BINARY_DIR}/hotreload.grpc.pb.h") add_custom_command(
  # OUTPUT "${hotreload_proto_srcs}" "${hotreload_proto_hdrs}"
  # "${hotreload_grpc_srcs}" "${hotreload_grpc_hdrs}" COMMAND
  # ${_PROTOBUF_PROTOC} ARGS --grpc_out "${CMAKE_CURRENT_BINARY_DIR}" --cpp_out
  # "${CMAKE_CURRENT_BINARY_DIR}" -I "${hotreload_proto_path}" --plugin=protoc-
  # gen-grpc="${_GRPC_CPP_PLUGIN_EXECUTABLE}" "${hotreload_proto}" DEPENDS
  # "${hotreload_proto}")

  # Include generated *.pb.h files
  # include_directories("${CMAKE_CURRENT_BINARY_DIR}")

  # some protobuf headers are still required even when using flatbuffer serialization.
  include_directories("${CMAKE_SOURCE_DIR}/externals/grpc/third_party/protobuf/src/")

  # gRPC header files.
  include_directories("${CMAKE_SOURCE_DIR}/externals/grpc/include")

  #
  # Experimental. Use flatbuffers for serialization
  #

  # [flatbuffers]
  set(FLATBUFFERS_BUILD_TESTS Off CACHE INTERNAL "" FORCE)
  set(FLATBUFFERS_BUILD_FLATHASH Off CACHE INTERNAL "" FORCE)
  set(FLATBUFFERS_INSTALL Off CACHE INTERNAL "" FORCE)

  add_subdirectory(${CMAKE_SOURCE_DIR}/externals/flatbuffers)

  # Flatbuffer header files.
  include_directories("${CMAKE_SOURCE_DIR}/externals/flatbuffers/include")

  # Assume `$BUILD/externals/flatbuffers/flatc`
  set(_FLATBUFFER_FLATC $<TARGET_FILE:flatc>)

  # Flatbuffer file
  get_filename_component(hotreload_fbs
                         "${CMAKE_SOURCE_DIR}/src/hotreload/hotreload.fbs"
                         ABSOLUTE)
  get_filename_component(hotreload_fbs_path "${hotreload_fbs}" PATH)

  # Generated sources
  set(hotreload_fb_hdrs "${CMAKE_CURRENT_BINARY_DIR}/hotreload_generated.h")
  set(hotreload_grpc_srcs "${CMAKE_CURRENT_BINARY_DIR}/hotreload.grpc.fb.cc")
  set(hotreload_grpc_hdrs "${CMAKE_CURRENT_BINARY_DIR}/hotreload.grpc.fb.h")
  add_custom_command(OUTPUT "${hotreload_fb_hdrs}" "${hotreload_grpc_srcs}"
                            "${hotreload_grpc_hdrs}"
                     COMMAND ${_FLATBUFFER_FLATC}
                             ARGS -o "${CMAKE_CURRENT_BINARY_DIR}"
                             --grpc -c "${hotreload_fbs}"
                     DEPENDS "${hotreload_fbs}")

  set(EXPORTER_LOGIC_PLUGIN_NAME "exporter_logic")

  add_library(${EXPORTER_LOGIC_PLUGIN_NAME}
              SHARED
              ./src/hotreload/HotReloadExporterLogic.cc
              ./src/hotreload/cyhair-writer.cc
              ${hotreload_fb_srcs}
              ${hotreload_grpc_srcs})

  # Must link with OpenMaya otherwise undefined symbol error happens when
  # loading dll(Linux only?).
  target_link_libraries(${EXPORTER_LOGIC_PLUGIN_NAME}
                        ${_GRPC_GRPCPP_UNSECURE}
                        flatbuffers
                        AdskXGen
                        OpenMaya
                        OpenMayaAnim # For SkinCluster
                        OpenMayaUI # For progress window
                        Foundation)