3.8.2/share/cmake-3.8/Modules/Platform/Darwin-Determine-CXX.cmake

if(NOT CMAKE_CXX_COMPILER_NAMES)
  set(CMAKE_CXX_COMPILER_NAMES c++)
endif()

# Exclude C++ compilers differing from C compiler only by case
# because this platform may have a case-insensitive filesystem.
set(CMAKE_CXX_COMPILER_EXCLUDE CC aCC xlC)