Linking external libraries and interfaces with CMake

[GreenGiant]

When using CMake to build a desktop programme, you can link in external libraries. For example, if I wanted to link in the jsoncpp library on linux (libjsoncpp-dev), my root CMakeLists.txt might look like:

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1. project(myprogram)
2. find_package(PkgConfig REQUIRED)
3. pkg_check_modules(JSONCPP jsoncpp)
4. link_libraries(${JSONCPP_LIBRARIES})
5. add_executable(myprogram myprogram.cpp)
6. target_link_libraries(myprogram ${JSONCPP_LIBRARIES}) # this must come after add_executable(...)

GeSHi © Codebox Plus Extension

With building using the IDF (I am on 4v3), we don't have the add_executable(...) command in our project, but I can see it in the project.cmake file in the IDF tools. https://github.com/espressif/esp-idf/bl ... cmake#L443

What would be the proper way to include & link external libraries into an IDF project?

Using jsoncpp as an example here which is a full library but I also want to use the GSL from Microsoft which is a header only interface.

When I say the "proper" way, I mean the CMake way. So that I can have a `libraries` directory in my project, with `git submodules` of all the libraries I want. As opposed to just copy and pasting source and header files from a library into my project, which is not as maintainable nor as elegant for open source projects.

Ref
jsoncpp: https://github.com/open-source-parsers/jsoncpp
GSL: https://github.com/microsoft/GSL

[ESP_Sprite]

Perhaps the build system docs have the info you need? For what it's worth, the way we tend to do this in Espressif is to create a component, put any files needed to properly compile the library in that component directory, then add the original, upstream library source tree in that component dir as a submodule (random example). Perhaps that works for you as well.

[GreenGiant]

Sprite, many thanks. No idea how I missed this in the docs, apologies.

So I have got the CMake side of things working now with GSL (interface, header only lib) and JsonCpp, using you suggestions.

If anyone reading is still struggling the commit is public, so hopefully this helps you out:
https://github.com/howroyd/esp32-serial ... 283e62749c