CODEWITHSUNDEEP
arraysfortranfortran-iso-c-bindingfortran2003
Demi
Demi

Reputation: 3611

How can I return an array from Fortran to C?

I am wondering what the correct way is to return an array from Fortran to C, using the ISO C bindings in Fortran.

Upvotes: 0

Views: 437

Answers (2)

bdforbes
bdforbes

Reputation: 1556

function return_an_array result(res) bind(c)
    use iso_c_binding

    implicit none

    interface
        function malloc(n) bind(c,name='malloc')
            use iso_c_binding
            type(c_ptr)::malloc
            integer(c_size_t),value::n
        end function malloc
    end interface

    type,bind(c)::c_array_2d
        type(c_ptr)::p
        integer(c_int)::dims(2)
    end type

    type(c_array_2d)::res
    integer(c_size_t)::res_len

    real(c_double),pointer::a(:,:)

    res_len = 3*2*c_double
    res%p = malloc(res_len)
    res%dims = [3, 2]

    call c_f_pointer(res%p, a, [2,3])

    a(1,1) = 1.0
    a(2,1) = 2.0
    a(1,2) = 3.0
    a(2,2) = 4.0
    a(1,3) = 5.0
    a(2,3) = 6.0

end function

Upvotes: 0

M. S. B.
M. S. B.

Reputation: 29401

Simple example:

#include <stdio.h>
#include <stdlib.h>

void F_sub ( float * array_ptr );

int main ( void ) {

   float * array_ptr;

   array_ptr = malloc (8);

   F_sub (array_ptr);

   printf ( "Values are: %f %f\n", array_ptr [0], array_ptr [1] );

   return 0;
}

and

subroutine F_sub ( array ) bind (C, name="F_sub")

   use, intrinsic :: iso_c_binding
   implicit none

   real (c_float), dimension (2), intent (out) :: array

   array = [ 2.5_c_float, 4.4_c_float ]

end subroutine F_sub

Upvotes: 1

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