生成的 PROTOBUF_INTERNAL_EXPORT 不包括导入的子目录

Question

为了让我的 proto 文件正确编译以便在我的 C++ 项目中使用，我付出了很多努力。从几个 stackoverflow 帖子中，我不得不尝试至少 8 种不同的方法，但都失败了。

目前，我收到一个错误：

‘PROTOBUF_INTERNAL_EXPORT_messages_2fbot_5farrived_2eproto’ does not name a type; did you mean ‘PROTOBUF_INTERNAL_EXPORT_bot_5farrived_2eproto’?

extern PROTOBUF_INTERNAL_EXPORT_messages_2fbot_5farrived_2eproto ::PROTOBUF_NAMESPACE_ID::internal::SCCInfo scc_info_BotArrived_messages_2fbot_5farrived_2eproto;

如果我从生成的 extern 中删除 messages_2f，它会起作用。为什么它没有正确地使用我从中导入的子目录生成内容？

我的 proto 文件已存储：

project
    protos
        message   # This imports all the concrete types using import "messages/<concretetype>
    messages
        bot_arrived.proto
        .... other concrete types
    CmakeLists.txt
    ...
        

我当前的 Frakenstein-ed cmake 文件部分（生成文件的位置）如下所示：

# Generated Proto files
file(GLOB_RECURSE proto_files "${CMAKE_CURRENT_SOURCE_DIR}/*.proto")

# Create an include path for each file specified
if(PROTOBUF_GENERATE_CPP_APPEND_PATH)
    foreach(FIL ${proto_files})
        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()

message(STATUS "Proto Include Path: ${protobuf_include_path}")

set(proto_srcs)
set(proto_hdrs)
set(grpc_proto_srcs)
set(grpc_proto_hdrs)
set(grpc_generated_include_paths "${CMAKE_CURRENT_BINARY_DIR}" CACHE STRING "Will be needed in the include path of targets that consume this lib")

foreach(FIL ${proto_files})
    get_filename_component(ABS_FIL ${FIL} ABSOLUTE)
    get_filename_component(FIL_WE ${FIL} NAME_WE)
    get_filename_component(DIR ${FIL} DIRECTORY)
    file(RELATIVE_PATH REL_DIR "${CMAKE_CURRENT_SOURCE_DIR}/protos/" ${DIR})

    if("${REL_DIR}" STREQUAL "")
        set(proto_src "${CMAKE_CURRENT_BINARY_DIR}/${FIL_WE}.pb.cc")
        set(proto_hdr "${CMAKE_CURRENT_BINARY_DIR}/${FIL_WE}.pb.h")
        set(grpc_proto_src "${CMAKE_CURRENT_BINARY_DIR}/${FIL_WE}.grpc.pb.cc")
        set(grpc_proto_hdr "${CMAKE_CURRENT_BINARY_DIR}/${FIL_WE}.grpc.pb.h")
        set(grpc_out_dir "${CMAKE_CURRENT_BINARY_DIR}")
    else()
        set(proto_src "${CMAKE_CURRENT_BINARY_DIR}/${REL_DIR}/${FIL_WE}.pb.cc")
        set(proto_hdr "${CMAKE_CURRENT_BINARY_DIR}/${REL_DIR}/${FIL_WE}.pb.h")
        set(grpc_proto_src "${CMAKE_CURRENT_BINARY_DIR}/${REL_DIR}/${FIL_WE}.grpc.pb.cc")
        set(grpc_proto_hdr "${CMAKE_CURRENT_BINARY_DIR}/${REL_DIR}/${FIL_WE}.grpc.pb.h")
        set(grpc_out_dir "${CMAKE_CURRENT_BINARY_DIR}/${REL_DIR}")
    endif()

    if( NOT EXISTS "${grpc_out_dir}" AND NOT IS_DIRECTORY "${grpc_out_dir}")
        file(MAKE_DIRECTORY "${grpc_out_dir}")
    endif()

    list(FIND grpc_generated_include_paths ${grpc_out_dir} contains_already)
    if(${contains_already} EQUAL -1)
        list(APPEND grpc_generated_include_paths ${grpc_out_dir})
    endif()

    list(APPEND proto_srcs "${proto_src}")
    list(APPEND proto_hdrs "${proto_hdr}")
    list(APPEND grpc_proto_srcs "${grpc_proto_src}")
    list(APPEND grpc_proto_hdrs "${grpc_proto_hdr}")

    add_custom_command(
        OUTPUT "${proto_src}" "${proto_hdr}" "${grpc_proto_src}" "${grpc_proto_hdr}"
        COMMAND ${Protobuf_PROTOC_EXECUTABLE}
        ARGS --grpc_out "${grpc_out_dir}"
        --cpp_out "${grpc_out_dir}"
        --plugin=protoc-gen-grpc=${GRPC_PLUGIN}
        ${protobuf_include_path} ${ABS_FIL}
        DEPENDS ${ABS_FIL} ${Protobuf_PROTOC_EXECUTABLE}
        COMMENT "Running gRPC C++ protocol buffer compiler on ${FIL}. Output going to ${grpc_out_dir}"
        VERBATIM)
endforeach()

set_source_files_properties(${proto_srcs} ${proto_hdrs} PROPERTIES SKIP_AUTOMOC TRUE)
set_source_files_properties(${proto_srcs} ${proto_hdrs} PROPERTIES GENERATED TRUE)

message(STATUS "Proto generated sources: ${proto_srcs}")
message(STATUS "Proto generated headers: ${proto_hdrs}")
message(STATUS "gRPC generated sources: ${grpc_proto_srcs}")
message(STATUS "gRPC generated headers: ${grpc_proto_hdrs}")
message(STATUS "gRPC generated include paths ${grpc_generated_include_paths}")

Answer 1

使用--proto_path= 有什么用？

参考：https://github.com/google/or-tools/blob/stable/cmake/cpp.cmake#L267