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cmakeincludeclang-tidy

Is there a way to get -isystem for FetchContent targets?

NO_SYSTEM_FROM_IMPORTED tells us that IMPORTED targets automagically get -isystem. Does that also hold for targets introduced to the project with FetchContent?

If not (I assume so due to having problems with clang-tidy warnings on fetched targets), what is the best way to get -isystem for such targets?

Solution

  • NO_SYSTEM_FROM_IMPORTED tells us that IMPORTED targets automagically get -isystem. Does that also hold for targets introduced to the project with FetchContent?

    No, because targets added by FetchContent are essentially added by add_subdirectory: they become targets to build (instead of just import) in the generated buildystem.

    If not (I assume so due to having problems with clang-tidy warnings on fetched targets), what is the best way to get -isystem for such targets?

    If you are using CMake 3.25 (cmake_minimum_required(VERSION 3.25)), you can use the SYSTEM argument of FetchContent_Declare, which was added in merge request #7399 by contributor daquexian.

    For users of CPM, I have given the CPM authors a heads up about this change here.

    There is also the new SYSTEM target property, which was added in merge request #7308 (also by daquexian). If SYSTEM is ON, the INTERFACE_INCLUDE_DIRECTORIES will be treated as system include directories.

    If your cmake_minimum_required(VERSION ...) is less than v3.25, then use this other answer.