Mixed-Language Programming

• Interoperability with C
  • Intrinsic Types
  • Derived Types and struct
  • Interoperable Global Variables
  • Interoperable Subroutines and Functions
  • Working with C Pointers
  • Further Interoperability of Fortran with C
• GNU Fortran Compiler Directives
  • ATTRIBUTES directive
  • UNROLL directive
  • BUILTIN directive
  • IVDEP directive
  • VECTOR directive
  • NOVECTOR directive
• Non-Fortran Main Program
  • _gfortran_set_args — Save command-line arguments
  • _gfortran_set_options — Set library option flags
  • _gfortran_set_convert — Set endian conversion
  • _gfortran_set_record_marker — Set length of record markers
  • _gfortran_set_fpe — Enable floating point exception traps
  • _gfortran_set_max_subrecord_length — Set subrecord length
• Naming and argument-passing conventions
  • Naming conventions
  • Argument passing conventions

This chapter is about mixed-language interoperability, but also applies if you link Fortran code compiled by different compilers. In most cases, use of the C Binding features of the Fortran 2003 and later standards is sufficient.

For example, it is possible to mix Fortran code with C++ code as well as C, if you declare the interface functions as extern "C" on the C++ side and BIND(C) on the Fortran side, and follow the rules for interoperability with C. Note that you cannot manipulate C++ class objects in Fortran or vice versa except as opaque pointers.

You can use the gfortran command to link both Fortran and non-Fortran code into the same program, or you can use gcc or g++ if you also add an explicit -lgfortran option to link with the Fortran library. If your main program is written in C or some other language instead of Fortran, see Non-Fortran Main Program, below.