Calling C function with **int parameter from Fortran

Question

Suppose that I have a C function with the following API :

int c_function(int **a);

How should I go about declaring a Fortran array/pointer to array, and passing it to the function, assuming that the C function is responsible for memory allocation ?

I don't think you can.

Iharob Al Asimi
– Iharob Al Asimi

2015-06-02 12:20:32 +00:00
Commented Jun 2, 2015 at 12:20 — Iharob Al Asimi
– Iharob Al Asimi, Commented Jun 2, 2015 at 12:20

Vladimir F Героям слава · Accepted Answer · 2015-06-02 19:53:25Z

4

You must declare a Fortan c-pointer of type(c_ptr)

type(c_ptr) :: ptr

then call your function (with proper interface)

n = c_function(ptr)

and only then point a Fortran array pointer there

real, pointer :: Array(:)

call c_f_pointer(ptr, Array, [n])

I assumed that n is the size of the array. You must know it, otherwise it is impossible.

The interface could look like

interface

    integer(c_int) function c_function(ptr) bind(C,name="c_function")
      use iso_c_binding
      type(c_ptr) :: ptr
    end function

end interface

edited Jun 2, 2015 at 19:53

answered Jun 2, 2015 at 13:23

Vladimir F Героям слава

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2 Comments

Vladimir F Героям слава Over a year ago

I couldn't find an exact duplicate, just this one stackoverflow.com/questions/30481686/… but that is not very good to point to. Feel free ti find better one.

Dooggy Over a year ago

Thank you, this works perfectly. Although if I'm printing the pointer in the C function, I get the same value for all the processes in my MPI communicator. But it somehow works.

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