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This was intended to be part of the initial MR (!6177), but accidentally went missing when debugging nightly failures on less common systems. Noticed during !6711 review as the comment about this behaviour didn't match the code. Documentation for CMP0128 is updated to remove a false case and note the two cases related to this. Fixes #22224.
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2.6 KiB
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72 lines
2.6 KiB
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CMP0128
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-------
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.. versionadded:: 3.22
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When this policy is set to ``NEW``:
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* :prop_tgt:`<LANG>_EXTENSIONS` is initialized to
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:variable:`CMAKE_<LANG>_EXTENSIONS` if set, otherwise falling back to
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:variable:`CMAKE_<LANG>_EXTENSIONS_DEFAULT`.
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* Extensions are correctly enabled/disabled if :prop_tgt:`<LANG>_STANDARD` is
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unset or satisfied by the default.
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* Standard mode-affecting flags aren't added unless necessary to achieve the
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specified mode.
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The ``OLD`` behavior:
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* Initializes :prop_tgt:`<LANG>_EXTENSIONS` to
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:variable:`CMAKE_<LANG>_EXTENSIONS` if set, otherwise falling back to ``ON``.
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* Always adds a flag if :prop_tgt:`<LANG>_STANDARD` is set and
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:prop_tgt:`<LANG>_STANDARD_REQUIRED` is ``OFF``.
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* If :prop_tgt:`<LANG>_STANDARD` is unset:
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* Doesn't disable extensions even if :prop_tgt:`<LANG>_EXTENSIONS` is
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``OFF``.
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* Fails to enable extensions if :prop_tgt:`<LANG>_EXTENSIONS` is ``ON``
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except for the ``IAR`` compiler.
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Code may need to be updated for the ``NEW`` behavior in the following cases:
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* If a standard mode flag previously overridden by CMake's and not used during
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compiler detection now takes effect due to CMake no longer adding one as the
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default detected is appropriate.
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Such code should be converted to either:
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* Use :prop_tgt:`<LANG>_STANDARD` and :prop_tgt:`<LANG>_EXTENSIONS` instead
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of manually adding flags.
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* Or ensure the manually-specified flags are used during compiler detection.
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* If extensions were disabled without :prop_tgt:`<LANG>_STANDARD` being set
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CMake previously wouldn't actually disable extensions.
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Such code should be updated to not disable extensions if they are required.
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* If extensions were enabled/disabled when :prop_tgt:`<LANG>_STANDARD` was
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satisfied by the compiler's default CMake previously wouldn't actually
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enable/disable extensions.
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Such code should be updated to set the correct extensions mode.
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If compiler flags affecting the standard mode are used during compiler
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detection (for example in :manual:`a toolchain file <cmake-toolchains(7)>`
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using :variable:`CMAKE_<LANG>_FLAGS_INIT`) then they will affect the detected
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default :variable:`standard <CMAKE_<LANG>_STANDARD_DEFAULT>` and
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:variable:`extensions <CMAKE_<LANG>_EXTENSIONS_DEFAULT>`.
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Unlike many policies, CMake version |release| does *not* warn when the policy
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is not set and simply uses the ``OLD`` behavior. Use the
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:command:`cmake_policy` command to set it to ``OLD`` or ``NEW`` explicitly.
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See documentation of the
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:variable:`CMAKE_POLICY_WARNING_CMP0128 <CMAKE_POLICY_WARNING_CMP<NNNN>>`
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variable to control the warning.
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.. include:: DEPRECATED.txt
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