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33 lines
1.4 KiB
33 lines
1.4 KiB
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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