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CMake Experimental Features Guide
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*********************************
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The following is a guide to CMake experimental features that are
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under development and not yet included in official documentation.
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See documentation on `CMake Development`_ for more information.
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.. _`CMake Development`: README.rst
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Features are gated behind ``CMAKE_EXPERIMENTAL_`` variables which must be set
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to specific values in order to enable their gated behaviors. Note that the
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specific values will change over time to reinforce their experimental nature.
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When used, a warning will be generated to indicate that an experimental
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feature is in use and that the affected behavior in the project is not part of
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CMake's stability guarantees.
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Export Package Dependencies
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===========================
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In order to activate support for this experimental feature, set
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* variable ``CMAKE_EXPERIMENTAL_EXPORT_PACKAGE_DEPENDENCIES`` to
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* value ``1942b4fa-b2c5-4546-9385-83f254070067``.
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This UUID may change in future versions of CMake. Be sure to use the value
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documented here by the source tree of the version of CMake with which you are
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experimenting.
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When activated, this experimental feature provides the following:
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* The ``install(EXPORT)`` and ``export(EXPORT)`` commands have experimental
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``EXPORT_PACKAGE_DEPENDENCIES`` arguments to generate ``find_dependency``
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calls automatically.
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* Details of the calls may be configured using the ``export(SETUP)``
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command's ``PACKAGE_DEPENDENCY`` argument.
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* The package name associated with specific targets may be specified
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using the ``CMAKE_EXPORT_FIND_PACKAGE_NAME`` variable and/or
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``EXPORT_FIND_PACKAGE_NAME`` target property.
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C++ ``import std`` support
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==========================
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In order to activate support for ``import std`` in C++23 and newer targets,
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set
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* variable ``CMAKE_EXPERIMENTAL_CXX_IMPORT_STD`` to
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* value ``0e5b6991-d74f-4b3d-a41c-cf096e0b2508``.
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This UUID may change in future versions of CMake. Be sure to use the value
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documented here by the source tree of the version of CMake with which you are
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experimenting. It must be set before the ``CXX`` toolchain is discovered by
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CMake, usually as part of a :command:`project` call.
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When activated, this experimental feature provides the following:
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* The :prop_tgt:`CXX_MODULE_STD` target property and its initializing variable
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:variable:`CMAKE_CXX_MODULE_STD`.
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* Targets with the property set to a true value and at least ``cxx_std_23``
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may use ``import std;`` in any scanned C++ source file.
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