Handling Integer Pointers

Integer pointers (also known as Cray*-style pointers) are not the same as Fortran 90 pointers, but are instead like C pointers. Integer pointers are 4-byte INTEGER quantities on IA-32 systems, and 8-byte INTEGER quantities on Itanium®-based systems.

Passing Integer Pointers

When passing an integer pointer to a routine written in another language:

For example:

! Fortran main program.
  INTERFACE
     SUBROUTINE Ptr_Sub (p)
    !DEC$ ATTRIBUTES C, ALIAS:'Ptr_Sub' :: Ptr_Sub
        INTEGER p
     END SUBROUTINE Ptr_Sub
  END INTERFACE
  REAL A(10), VAR(10)
  POINTER (p, VAR) ! VAR is the pointee
                   ! p is the integer pointer
  p = LOC(A)
  CALL Ptr_Sub (p)
  WRITE(*,*) 'A(4) = ', A(4)
 END
!
//C subprogram
  void Ptr_Sub (float *p)
  {
    p[3] = 23.5;
  }

On Itanium-based systems, the declaration for p in the INTERFACE block should be INTEGER(8) p.

When the main Fortran program and C function are built and executed, the following output appears:

A(4) = 23.50000

Receiving Pointers

When receiving a pointer from a routine written in another language:

For example:

! Fortran subroutine.
  SUBROUTINE Iptr_Sub (p)
  !DEC$ ATTRIBUTES C, ALIAS:'Iptr_Sub' :: Iptr_Sub
     integer VAR(10)
     POINTER (p, VAR)
     OPEN (8, FILE='STAT.DAT')
     READ (8, *) VAR(4) ! Read from file and store the
                        ! fourth element of VAR      
END SUBROUTINE Iptr_Sub
!
//C main program
extern void Iptr_Sub(int *p);
main ( void ) {   int a[10];
Iptr_Sub (&a[0]);
printf("a[3] = %i\n", a[3]);
}

When the main C program and Fortran subroutine are built and executed, the following output appears if the STAT.DAT file contains 4:

   a[3] = 4