Compiler id for Apple Clang is now
CMake 3.0 and above recognize that Apple Clang is a different compiler than upstream Clang and that they have different version numbers. CMake now prefers to present this to projects by setting the
CMAKE_<LANG>_COMPILER_ID variable to
AppleClang instead of
Clang. However, existing projects may assume the compiler id for Apple Clang is just
Clang as it was in CMake versions prior to 3.0. Therefore this policy determines for Apple Clang which compiler id to report in the
CMAKE_<LANG>_COMPILER_ID variable after language
<LANG> is enabled by the
enable_language command. The policy must be set prior to the invocation of either command.
The OLD behavior for this policy is to use compiler id
Clang. The NEW behavior for this policy is to use compiler id
This policy was introduced in CMake version 3.0. Use the
cmake_policy command to set this policy to OLD or NEW explicitly. Unlike most policies, CMake version does not warn by default when this policy is not set and simply uses OLD behavior. See documentation of the
CMAKE_POLICY_WARNING_CMP0025 <CMAKE_POLICY_WARNING_CMP<NNNN>> variable to control the warning.