# protobuf\_generate\_cpp: version in repo won't generate grpc files

**URL:** <https://discourse.cmake.org/t/protobuf-generate-cpp-version-in-repo-wont-generate-grpc-files/6000>\
**Category:** Code\
**Tags:** gen:makefiles\
**Created:** [July 5, 2022, 5:23am UTC](https://discourse.cmake.org/t/protobuf-generate-cpp-version-in-repo-wont-generate-grpc-files/6000 "2022-07-05T05:23:08Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![JRHeisey](https://discourse.cmake.org/letter_avatar_proxy/v4/letter/j/f07891/32.png) [@JRHeisey](https://discourse.cmake.org/u/JRHeisey)\
**Post date:** [July 5, 2022, 5:23am UTC](https://discourse.cmake.org/t/protobuf-generate-cpp-version-in-repo-wont-generate-grpc-files/6000/1 "2022-07-05T05:23:08Z")

</div>

- I want to use CMake to use protoc to generate the RPC files for cpp
- I am generating make files
- I enable various tracing outputs
- I can see the CMake flags --grpc\_out and --plugin in the CMake putput
- The CMake generated build.make file does not contain these flags
- Below are relevant snippets from CMake and FindProtobuf.cmake
- I made a project specific copy of FindProtobuf.cmake because the one  
in the kitware repo contains a way to enable --grpc\_out.
- I need both the generated gRPC client and server code

Does anyone have any suggestions?

```auto
// CMakeLists.txt
# =============================================================
# Protobuf
# =============================================================
list(APPEND CMAKE_PREFIX_PATH "/usr/local/protobuf-3.3.0/")

set(Protobuf_USE_STATIC_LIBS ON)
set(Protobuf_DEBUG 1)
set(protobuf_generate_PLUGIN "${GRPC_CPP_PLUGIN_EXECUTABLE}")
include(cmake/FindProtobuf.cmake)
FIND_PACKAGE(Protobuf 3.3.0 REQUIRED)

set(GENERATED_PROTOS_DIR ${CMAKE_CURRENT_BINARY_DIR}/generated)
file(MAKE_DIRECTORY ${GENERATED_PROTOS_DIR})
include_directories(${GENERATED_PROTOS_DIR})

protobuf_generate_cpp( GEN_PROTO_SRCS_CPP GEN_PROTO_HDRS_CPP 
                       IMPORT_DIRS ${PROTO_PATHS} 
                       PROTOS ${PROTO_FILE}
                     )

add_library(${PROJECT_NAME} SHARED
            ${GEN_PROTO_SRCS_CPP} ${GEN_PROTO_HDRS_CPP}
            src/FooInterface.cpp
            )

// FindProtobuf.cmake found here
// https://github.com/Kitware/CMake/blob/master/Modules/FindProtobuf.cmake

// Latest from the repo contains
  if(protobuf_generate_PLUGIN)
    set(_plugin "--plugin=${protobuf_generate_PLUGIN}")
  endif()
// then
    add_custom_command(
      OUTPUT ${_generated_srcs}
      COMMAND protobuf::protoc
      ARGS --${protobuf_generate_LANGUAGE}_out ${_dll_export_decl}${protobuf_generate_PROTOC_OUT_DIR} ${_plugin} ${_dll_desc_out} ${_protobuf_include_path} ${_abs_file}
      DEPENDS ${_abs_file} protobuf::protoc
      COMMENT "Running ${protobuf_generate_LANGUAGE} protocol buffer compiler on ${_proto}"
      VERBATIM )

// running cmake3 output

-- OUTPUT FooServices.grpc.pb.cc FooServices.grpc.pb.h

-- COMMAND /usr/local/protobuf-3.3.0/bin/protoc --grpc_out /user/me/ProjectFoo/build/default --cpp_out /user/me/ProjectFoo/build/default -I /user/me/ProjectFoo/src --plugin=protoc-gen-grpc=/usr/local/bin/grpc_cpp_plugin
-- DEPENDS /user/me/ProjectFoo/src/FooServices.proto
-- GEN_PROTO_SRCS_CPP=/user/me/ProjectFoo/build/default/FooServices.pb.cc GEN_PROTO_SRCS_PY=
-- UTIL_LIB_PATH=/build
-- Protobuf_LIBRARIES=/usr/local/protobuf-3.3.0/lib/libprotobuf.a;-lpthread

// running make output 
[25%] Running cpp protocol buffer compiler on /user/me/ProjectFoo/foo-interface/src/FooServices.proto
/usr/local/protobuf-3.3.0/bin/protoc --cpp_out /user/me/ProjectFoo/foo-interface/build/default -I /user/me/ProjectFoo/foo-interface/src /user/me/ProjectFoo/foo-interface/src/FooServices.proto

// from generated build.make
CMakeFiles/foo-interface.dir/build.make:	/usr/local/protobuf-3.3.0/bin/protoc --cpp_out /user/me/ProjectFoo/foo-interface/build/default -I /user/me/ProjectFoo/foo-interface/src /user/me/ProjectFoo/foo-interface/src/FooServices.proto

```

---

<div class="post-metadata">

**Author:** ![hsattler](https://discourse.cmake.org/letter_avatar_proxy/v4/letter/h/59ef9b/32.png) [@hsattler](https://discourse.cmake.org/u/hsattler)\
**Post date:** [July 5, 2022, 6:06am UTC](https://discourse.cmake.org/t/protobuf-generate-cpp-version-in-repo-wont-generate-grpc-files/6000/2 "2022-07-05T06:06:26Z")

</div>

Did you add the generated files in GEN\_PROTO\_SRCS\_CPP variable to any target?

---

<div class="post-metadata">

**Author:** ![JRHeisey](https://discourse.cmake.org/letter_avatar_proxy/v4/letter/j/f07891/32.png) [@JRHeisey](https://discourse.cmake.org/u/JRHeisey)\
**Post date:** [July 5, 2022, 10:47pm UTC](https://discourse.cmake.org/t/protobuf-generate-cpp-version-in-repo-wont-generate-grpc-files/6000/3 "2022-07-05T22:47:27Z")

</div>

For an unknown reason my edits were flagged to be reviewed by an administrator.  
Therefore my posting wasn’t visible for a while and I could not edit it further until now.

@hsattler Yes GEN\_PROTO\_SRCS\_CPP was later reference in add\_library()

I have fully resolved all of my issues.

- I was calling `Find_Package(Protobuf 3.3.0 REQUIRED)` which includes the standard `FindProtobuf.cmake`
- The include of my own custom `FindProtobuf.cmake` occurred after the call to `Find_Package()`
- The custom `protobuf_generate*` functions were being overridden by the standard versions
- I reversed the order so that `Find_Package()` call is first.
- The newer `FindProtobuf.cmake` from which I based my custom version does not support the `--grpc_out` flag which is required for the `--plugin=protoc-gen-grpc` to perform the gRPC generation
- I temporarily hardcoded the `--grpc_out` parameter in my custom `FindProtobuf.cmake`

**Additional**

- The `protobuf_generate()` function has a `PLUGIN` parameter.
- The `protobuf_generate_cpp()` function does NOT have a `PLUGIN` parameter.
- The way function parameter are implemented is not clear to me so it may take me some time to figure out a more generic solution.

---

<div class="post-metadata">

**Author:** ![demonstrate](https://discourse.cmake.org/user_avatar/discourse.cmake.org/demonstrate/32/3172_2.png) [@demonstrate](https://discourse.cmake.org/u/demonstrate)\
**Post date:** [February 16, 2023, 12:32am UTC](https://discourse.cmake.org/t/protobuf-generate-cpp-version-in-repo-wont-generate-grpc-files/6000/4 "2023-02-16T00:32:02Z")

</div>

I wish this could be fixed earlier.

> [@JRHeisey](#):
>
> The `protobuf_generate_cpp()` function does NOT have a `PLUGIN` parameter.

To @JRHeisey I think what you said is not true here. The implementation has `protobuf_generate_cpp_UNPARSED_ARGUMENTS` after calling `cmake_parse_argument` and passed into the `protobuf_generate` function as `${_proto_files}`. So if you have `PLUGIN ...` there, it should still work as expected.

The real issue is that we have no way to add `--grpc_out` to the `ARGS` in the `add_custom_command`. The implementation doesn’t seem to have a way to tell (in a generic way) what kind of plugin is provided and whether it would be correct to add extra flags to the `protoc` command.

Perhaps checking `protobuf_generate_PLUGIN` would be a way

```auto
  set(_plugin)
  if(protobuf_generate_PLUGIN)
    LIST(APPEND _plugin "--plugin=${protobuf_generate_PLUGIN}")
    string(FIND "${protobuf_generate_PLUGIN}" "protoc-gen-grpc" _grpc_found)
    if(_grpc_found GREATER -1)
      list(APPEND _plugin "--grpc_out" "${protobuf_generate_PROTOC_OUT_DIR}")
    endif()
  endif()

```

then the user can just call

```auto
protobuf_generate_cpp(
  helloworld_proto_srcs
  helloworld_proto_hdrs
  helloworld.proto
  PLUGIN "protoc-gen-grpc=${_GRPC_CPP_PLUGIN_EXECUTABLE}"
  GENERATE_EXTENSIONS .pb.h .pb.cc .grpc.pb.h .grpc.pb.cc
)

```