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Extend the documentation added by commit 96a7040107 (project: Define
variables indicating whether project is top level, 2021-03-24,
v3.21.0-rc1~443^2) to give some examples of how the variables are set in
each context.
32 lines
875 B
ReStructuredText
32 lines
875 B
ReStructuredText
PROJECT_IS_TOP_LEVEL
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--------------------
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.. versionadded:: 3.21
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A boolean variable indicating whether :command:`project` was called in a top
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level ``CMakeLists.txt`` file.
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Some modules should only be included as part of the top level
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``CMakeLists.txt`` file to not cause unintended side effects in the build
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tree, and this variable can be used to conditionally execute such code. For
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example, consider the :module:`CTest` module, which creates targets and
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options:
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.. code-block:: cmake
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project(MyProject)
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...
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if(PROJECT_IS_TOP_LEVEL)
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include(CTest)
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endif()
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The variable value will be true in:
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* the top-level directory of the project
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* the top-level directory of an external project added by :module:`ExternalProject`
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The variable value will be false in:
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* a directory added by :command:`add_subdirectory`
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* a directory added by :module:`FetchContent`
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