Interfacing with C Code

This example demonstrates how to call C functions from Fortran.

fortranCopy codemodule interface
    use iso_c_binding, only: c_int, c_double, c_null_ptr, c_f_pointer
    implicit none

    interface
        function c_function(x) bind(c)
            import :: c_double
            real(c_double) :: c_function
            real(c_double), value :: x
        end function c_function
    end interface

end module interface

program call_c
    use interface
    implicit none
    real(c_double) :: result

    result = c_function(3.0)
    print *, 'Result from C function: ', result
end program call_c

In the above example, you would need a C function defined as follows and compiled with the Fortran code:

cCopy code#include <stdio.h>

double c_function(double x) {
    return x * x;
}

Compile the C code into a shared library and link it with the Fortran program.