| 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:: STANDARD_ADVICE.txt |
| |
| .. include:: DEPRECATED.txt |
