CMAKE_EXPERIMENTAL_CXX_IMPORT_STD value history and state

Development
1

AFAIK, this is are the current rules to activate import std; with last stable CMake versions:

if(CMAKE_VERSION VERSION_GREATER_EQUAL "3.30.0")
    if(CMAKE_VERSION VERSION_LESS "3.31.8")
        set(CMAKE_EXPERIMENTAL_CXX_IMPORT_STD
            "0e5b6991-d74f-4b3d-a41c-cf096e0b2508"
        )
    elseif(CMAKE_VERSION VERSION_LESS "4.0.0")
        set(CMAKE_EXPERIMENTAL_CXX_IMPORT_STD
            "d0edc3af-4c50-42ea-a356-e2862fe7a444"
        )
    elseif(CMAKE_VERSION VERSION_LESS "4.0.3")
        set(CMAKE_EXPERIMENTAL_CXX_IMPORT_STD
            "a9e1cf81-9932-4810-974b-6eccaf14e457"
        )
    elseif(CMAKE_VERSION VERSION_LESS "4.3.0")
        set(CMAKE_EXPERIMENTAL_CXX_IMPORT_STD
            "d0edc3af-4c50-42ea-a356-e2862fe7a444"
        )
    elseif(CMAKE_VERSION VERSION_LESS "4.4.0")
        set(CMAKE_EXPERIMENTAL_CXX_IMPORT_STD
            "451f2fe2-a8a2-47c3-bc32-94786d8fc91b"
        )
    endif()
endif()
  • Is it really necessary to change the UUID in this way?
  • What is planed to be the right value for CMake v4.4.0?
  • I wonder if a UUID value from the experimental gate must be changed at all?
2

Anytime we change the behavior of the experimental feature, the UUID is recycled. This is because behavior changes can break existing code, contrary to CMake’s typical compatibility guarantees.

I’m not aware of any pending changes that would change 4.4’s UUID, but that doesn’t mean we won’t fix bugs (and change the UUID in the process) if they come up.

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