CMake: How to add custom generic compilation rule?

Question

I need to compile protocol buffer .proto files to .pb.cc,.pb.h files. There is a program for this conversion.

protoc test.proto --cpp_out .

How can I add such a generic rule in cmake? I can do this with add_custom_command. But I have to this for every .proto file. Is there a better way to do this?

Answer 1

It looks like CMake's FindProtobuf module provides this functionality via the function PROTOBUF_GENERATE_CPP.

You can pass multiple .proto files in the one call, e.g.

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

Note that even though the CMakeLists.txt file which calls find_package(Protobuf) could be the top-level one, the CMakeLists.txt file(s) which invoke the function would need to be in the same directory as the .proto files.