Compiling protobuf files with project build

[szabiaura]

Hi,

I have a bunch of .proto files that I want to compile with protobuf-c whenever the project is built. I want to make a component from it. I tried adding the following to my CMakeLists.txt:

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1. cmake_minimum_required(VERSION 3.5)
2.  
3. set(PROTO_COMPILER "protoc")
4. set(PROTO_C_COMPILER "protoc-c")
5. set(C_OUT_PATH "${CMAKE_CURRENT_LIST_DIR}/proto-c")
6.  
7. set(PROTO_SRCS "${CMAKE_CURRENT_LIST_DIR}/proto/Device.proto"
8.                "${CMAKE_CURRENT_LIST_DIR}/proto/Output.proto")
9.  
10. set(pb_csrcs
11.     "proto-c/Device.pb-c.c"
12.     "proto-c/Output.pb-c.c")
13.  
14. if(NOT CMAKE_BUILD_EARLY_EXPANSION)
15.     add_custom_command(OUTPUT ${pb_csrcs}
16.          COMMAND ${PROTO_C_COMPILER} --c_out=${C_OUT_PATH} -I . ${PROTO_SRCS}
17.          DEPENDS ${PROTO_SRCS}
18.          VERBATIM)
19. endif()
20.  
21. idf_component_register(SRCS "${pb_csrcs}"
22.                        INCLUDE_DIRS "proto-c"
23.                        REQUIRES protobuf-c)
24.  

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Bit it doesn't work, build fails with this error:

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1. -- Configuring done
2. CMake Error at /Users/cc/esp/esp-idf/tools/cmake/component.cmake:468 (add_library):
3.   Cannot find source file:
4.  
5.     /Users/cc/Documents/myproject/components/LEDBridgeProto/proto-c/Device.pb-c.c
6.  
7.   Tried extensions .c .C .c++ .cc .cpp .cxx .cu .m .M .mm .h .hh .h++ .hm
8.   .hpp .hxx .in .txx

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How is this possible? Shouldn't add_custom_command tell CMake how to build Device.pb-c.c?

Anybody has a good practice for compiling proto files during project build?

Thanks,
--
Szabi

[szabiaura]

Found the problem. Paths in pb_csrcs are relative to the build directory, whereas filenames in the SRCS option for idf_component_register are relative to the source directory. To fix, change lines 10-12 to

Code: [Select all] [Expand/Collapse]

1. set(pb_csrcs
2.     "${C_OUT_PATH}/Device.pb-c.c"
3.     "${C_OUT_PATH}/Output.pb-c.c")

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[ESP_Angus]

Hi Szabi,

Glad to hear that you found the solution.

Angus

[romaindequidt]

@szabiaura,
Do you have any examples on github (or anything else) to hava a look at your CMakeLists.txt?

Or, at least, can you copy paste:
- components/LEDBridgeProto/proto/CMakeListst.txt
- components/LEDBridgeProto/CMakeListst.txt

I have a lot of difficulty to trigger the proto file compilation.

Thanks in advance,