ad3c2c0b03
Every policy's documentation has a paragraph on what version of CMake introduced it, how to set the policy, and whether CMake warns if the policy is not set. The wording of this paragraph has diverged across policies over time. Factor the paragraph out into a standard advice document included by every policy.
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2.2 KiB
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54 lines
2.2 KiB
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CMP0149
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-------
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.. versionadded:: 3.27
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:ref:`Visual Studio Generators` select latest Windows SDK by default.
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Visual Studio Generators select a Windows SDK version to put in the
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``WindowsTargetPlatformVersion`` setting in ``.vcxproj`` files.
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CMake sets the :variable:`CMAKE_VS_WINDOWS_TARGET_PLATFORM_VERSION`
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variable to the selected SDK version.
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Prior to CMake 3.27, the SDK version was always selected by the value of
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the :variable:`CMAKE_SYSTEM_VERSION` variable. Users or toolchain files
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could set that variable to one of the exact Windows SDK versions available
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on the host system. Since :variable:`CMAKE_SYSTEM_VERSION` defaults to
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:variable:`CMAKE_HOST_SYSTEM_VERSION`, and it is not guaranteed that a
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matching Windows SDK version is available, CMake had to fall back to
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using the latest Windows SDK version if no exact match was available.
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This approach was problematic:
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* The latest Windows SDK might or might not be selected based on whether
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the host version of Windows happens to match an available SDK version.
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* An old Windows SDK version might be selected that has not been updated
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for newer language standards such as C11.
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CMake 3.27 and higher prefer to ignore the exact value of
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:variable:`CMAKE_SYSTEM_VERSION` and by default select the latest SDK
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version available. An exact SDK version may be specified explicitly
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using a ``version=`` field in the :variable:`CMAKE_GENERATOR_PLATFORM`
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variable. See :ref:`Visual Studio Platform Selection`.
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This policy provides compatibility for projects, toolchain files, and
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build scripts that have not been ported away from using
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:variable:`CMAKE_SYSTEM_VERSION` to specify an exact SDK version.
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.. note::
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This policy must be set before the first :command:`project` or
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:command:`enable_language` command invocation at the top of the
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project. That is when :ref:`Visual Studio Generators` select a
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Windows SDK.
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The ``OLD`` behavior for this policy is to use the exact value of
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:variable:`CMAKE_SYSTEM_VERSION` if possible. The ``NEW`` behavior
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for this policy is to ignore it.
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.. |INTRODUCED_IN_CMAKE_VERSION| replace:: 3.27
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.. |WARNS_OR_DOES_NOT_WARN| replace:: does *not* warn
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.. include:: STANDARD_ADVICE.txt
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.. include:: DEPRECATED.txt
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