The preprocessor definitions are defined at configure time by CMake in CMakeLists.txt and are passed on to the preprocessor. The Fortran example contains a very compact expression where we use the CMAKE_Fortran_COMPILER_ID variable to construct the preprocessor definition using target_compile_definitions. To accommodate this, we had to change the case of "Intel" from IS_INTEL_CXX_COMPILER to IS_Intel_FORTRAN_COMPILER. We could achieve the same for C or C++ by using the corresponding CMAKE_C_COMPILER_ID and CMAKE_CXX_COMPILER_ID variables. Please do note, however, that CMAKE_<LANG>_COMPILER_ID is not guaranteed to be defined for all compilers or languages.
Use the .F90 suffix for Fortran code that is supposed to be preprocessed ...
