Trying to pass strings to Fortan routines

[Jack Scheible <vze26j9s@mail.verizon.net>]

One of the promises of Ada was that one could use old libraries with the
Interfaces packages.  It's not going so well.  I have some old FORTRAN
libraries, and some of the routine accept CHARACTER*(*) arguments.  When
FORTRAN makes a subprogram call with one or more "string" arguments, it
passes the lengths of those strings as arguments _after_ all the
declared arguments.  I can get this to work with C.  So if I call

      SUBROUTINE SUB( S1, S2 )
      CHARACTER*(*) S1, S2

with the C statement

      sub_( s1, s2, strlen(s1), strlen(s2) );

All is well.  If I try the same thing in Ada (gnat), I get a Constraint
Error exception.

Actually, I get a Constraint Error if I just pass a String and anything
else.

Any ideas?

Thanks.

-jack