Utility to generate Fortran interface for C prototypes?

Help
1

Is there any (easy) working utility to generate Fortran interfaces, using iso_c_binding module, for a set of C prototypes, say placed in a C header file?

I have googled and found

  1. bindGen.rb - Ruby script in CDI package, does not seem to process my header
  2. h2m - I am unable to build it (it seems to require clang and llvm)
  3. cfwrapper.py by @vmagnin in gtk-fortran - this seems to be for gtk libraries only?
2

Yes, it was specifically developed to generate Fortran interfaces for GLib/GTK. You could of course hack it for other C libraries, but would have to finely tweak the code, especially the regular expressions. It depends on the complexity of the header files; the wrapper makes a first pass to clean the C preprocessor stuff before looking for C prototypes.

For C++, there is also GitHub - swig-fortran/swig: This fork of SWIG creates Fortran wrapper code from C++ headers.

I know also GitHub - eliben/pycparser: 🐍 Complete C99 parser in pure Python
Maybe it could be used to generate Fortran interfaces?

3

The difficulty of parsing C is that its syntax is quite versatile, and moreover it is a 2in1 language: the C language plus the C preprocessor.

Working recently on the next gtk-fortran release (GTK 4.10 / GLib 2.76), I have stumbled on a few functions like:

gboolean (g_str_has_suffix) (const gchar *str, const gchar *suffix);

I had already encountered such a syntax at the beginning of the project without understanding what it meant. That’s again a preprocessor trick: if you define a macro with that same name g_str_has_suffix, the preprocessor won’t make the substitution here because of the parentheses.
Of course, my wrapper “thought” that the name of the function was gboolean. I have refactored that part of the code and tune the regexes. Now, the analysis starts from the end of the line: the first parentheses pair (from right) is then the arguments of the function, then you have the name (possibly in parentheses), then the returned type.

4

My prototypes are very simple. No preprocessor directives, no abstract types, * character in pointer declarators always joining the identifier.

5

CBFortran (“fork” of CodeBlocks) or just CodeBlocks with “FortranProject” extension installed has some feature like described in tutorial: BindTo User Guide | CBFortran

Maybe it could be usefull in your case.

1 Like
6

It seems to work only one way “Fortran to C”, i.e. generating interfaces to call Fortran procedures from C

7

If you tell me the name of the library or if you send me the header files, I could try to use my cfwrapper on it. No guarantee, but if the prototypes are clear, we could expect a good result (partial or full).

8

SWIG linked upthread should work for your case.

9

FWIW, ChatGPT (specifically, GPT-4) does a surprisingly reasonable job generating Fortran interfaces and test code to call C functions (at least a few that I tried). I guess this question is asked often enough to provide lots of training material for it.

1 Like