Fortran 77 pointers

["E. Robert Tisdale" <edwin at netwood dot net>]

c       $ uname -m -r -s -v
c       Linux 2.0.36 #1 Tue Oct 13 22:17:11 EDT 1998 i686
c       $ g77 --version
c       egcs-2.90.29 980515 (egcs-1.0.3 release)
c       $ g77 -O2 -fno-globals -o gsl_pointer gsl_pointer.F gsl_address__.o
c
c       gsl_pointer.F
#define gsl_double  double precision
#define gsl_pointer integer
#define gsl_storage character
c
      subroutine f(x)
        gsl_double x
        write(*,*) x
        end
c
      subroutine g(p)
        gsl_pointer p
        gsl_storage gsl_memory_start(1)
        common /gsl_memory_space/gsl_memory_start
        gsl_pointer gsl_address
        gsl_pointer q
        q = 1 + p - gsl_address(gsl_memory_start)
        call f(gsl_memory_start(q))
        end
c
      program main
        gsl_storage gsl_memory_start(1)
        common /gsl_memory_space/gsl_memory_start
        gsl_pointer gsl_address
        gsl_double x
        x = 36.0
        call g(gsl_address(x))
        end
c
c       /* gsl_address__.c */
c       typedef int     gsl_pointer;
c       typedef char    gsl_storage;
c
c       gsl_pointer gsl_address__(gsl_storage* ps) {
c         return (gsl_pointer)ps;
c         }