1.3. Preprocessing and conditional compilation

1.3 Preprocessing and conditional compilation

Many Fortran compilers including GNU Fortran allow passing the source code through a C preprocessor (CPP; sometimes also called the Fortran preprocessor, FPP) to allow for conditional compilation. In the case of GNU Fortran, this is the GNU C Preprocessor in the traditional mode. On systems with case-preserving file names, the preprocessor is automatically invoked if the filename extension is .F, .FOR, .FTN, .fpp, .FPP, .F90, .F95, .F03 or .F08. To manually invoke the preprocessor on any file, use -cpp, to disable preprocessing on files where the preprocessor is run automatically, use -nocpp.

If a preprocessed file includes another file with the Fortran IN