@Alberto; ISO_C_BINDING + Doxygen parser:
Alberto, you are of course right that the intrinsic Fortran 2003 module ISO_C_BINDING solves the problem of name mangling and knowing the right C types for the corresponding Fortran types. But if one is bound to older Fortran standards this is not an option. I also tried to “misuse” Doxygen for what I want to accomplish but instead of touching the parser code, I looked into transforming Doxygen’s XML output to C declarations. But it seemed that the types of function parameters weren’t available in the XML output. So I also skipped this option.

@PeterP; DWARF debugging infos:
Using debugging infos from object files to create source code is another interesting idea. I actually wrote a simple and half done script (dwarf2cdecl.py) that can extract functions with their parameters from the output of dwarfdump -di. However, I think that this approach is to fragile and not as straightforward as I’d like it.

So I’m still open to suggestions.

It should be straightforward to convert this into the corresponding C declarations.
As the info comes from the object file, this also means that the mapping from unmangled to mangled names must be in the file, too (otherwise source code debugging would not work), courtesy of your compiler!

1. Name mangling, different between compilers.
2. Writing the prototype.

In order to solve the first, consider using the new ISO C bindings. Take a look from the page 31 in ftp://ftp.nag.co.uk/sc22wg5/N1601-N1650/N1648.pdf .

The second part would be a matter of writing a filter, or learning from Doxygen code how it parses Fortran structures.