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