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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.
33 lines
1.4 KiB
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33 lines
1.4 KiB
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CMP0123
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-------
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.. versionadded:: 3.21
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``ARMClang`` cpu/arch compile and link flags must be set explicitly.
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CMake 3.20 and lower automatically maps the :variable:`CMAKE_SYSTEM_PROCESSOR`
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variable and an undocumented ``CMAKE_SYSTEM_ARCH`` to compile and link options
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for ``ARMClang``. For example, the ``-mcpu=cortex-m33`` flag is added when
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:variable:`CMAKE_SYSTEM_PROCESSOR` equals ``cortex-m33``. CMake requires
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projects to set either variable or it raises a fatal error. However, the
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project may need to additionally specify CPU features using e.g.
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``-mcpu=cortex-m33+nodsp``, conflicting with the ``-mcpu=cortex-m33`` added
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by CMake. This results in either link errors or unusable binaries.
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CMake 3.21 and above prefer instead to not add any cpu/arch compile and link
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flags automatically. Instead, projects must specify them explicitly.
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This policy provides compatibility for projects that have not been updated.
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The ``OLD`` behavior of this policy requires projects that use ``ARMClang``
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to set either :variable:`CMAKE_SYSTEM_PROCESSOR` or ``CMAKE_SYSTEM_ARCH``
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and it automatically adds a compile option ``-mcpu=`` or ``-march=`` and
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a link option ``--cpu=`` based on those variables. The ``NEW`` behavior
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does not add compile or link options, and projects are responsible for
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setting correct options.
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.. |INTRODUCED_IN_CMAKE_VERSION| replace:: 3.21
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.. |WARNS_OR_DOES_NOT_WARN| replace:: warns
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.. include:: STANDARD_ADVICE.txt
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.. include:: DEPRECATED.txt
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