gfortran question about optional subroutine arguments

[Mark Hounschell <markh@xxxxxxxxxx>]

From what I read, what I need to do is doable in f90/f95 using optional 
arguments? But I am porting some very old fortran77 stuff and am using 
the -std=legacy switch. I'm basically trying to figure out how to call a 
subroutine with fewer arguments than the subroutine was declared with. 
The call works but in the code below I get a segfault when the 
subroutine attempts to access the unpassed argument. The old fortan77 
had no problems with this, I assume because even when not passed in, the 
subroutine declaration gave the argument a valid address??

      program test
      implicit none

      integer*4 arg1 /10/
      integer*4 arg2 /20/

      call sub1(arg1)
c    the old fortran77 call would have been
c    call sub1(arg1,)
      stop
      end

      subroutine sub1(arg1, arg2)
      implicit none

      integer*4 arg1
      integer*4 arg2

      arg2 = 0     ! causes segfault in gfortran
c
c    A segfault also occurs in some_other_sub if arg2 is accessed.
c
      call some_other_sub(arg1,arg2)  !

      return
      end

Yet a loc(arg2) any where is the line _seems_ to provide a valid address???

Is there a way this be done using -std=legacy switch


Thanks and Regards
Mark