Strings of dynamic length are always a bit tricky with the C interaction. A possible solution is to use pointers. First a simple case, where you have to hand over a null-character terminated string to a C-Function. If you really pass the string only in, you have to ensure to finalize it with the c_null_char, … Read more
Under the rules of current Fortran (Fortran 2008, but this is the same for when C interoperability was introduced in Fortran 2003), a Fortran procedure is not interoperable with C if it has an assumed shape dummy argument (other restrictions also apply). In your code degC, the dummy argument in the function DegCtoF, declared as … Read more
Here’s a minimum working example. I used gfortran and wrote the compile commands directly into the setup file. gfunc.f90 module gfunc_module implicit none contains subroutine gfunc(x, n, m, a, b, c) double precision, intent(in) :: x integer, intent(in) :: n, m double precision, dimension(n), intent(in) :: a double precision, dimension(m), intent(in) :: b double precision, … Read more
The way to do this now is to use the Fortran ISO C Binding on the Fortran side. This is part of the Fortran 2003 language standard and is available in many compilers; it is not specific to gcc. It has been described in many answers on this site. As part of the language standard, … Read more