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
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
<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
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 3.7.1 does not warn
by default when this policy is not set and simply uses OLD behavior.
See documentation of the
variable to control the warning.
OLD behavior of a policy is
deprecated by definition
and may be removed in a future version of CMake.