How to call Fortran routine in static library using C

What is the proper calling convention for a C routine to call a Fortran subroutine containing a character variable in the call list.

Example C code:
...
char *strng[1];
fsubr(strng[0]);
...

Example Fortran code:
SUBROUTINE FSUBR(strng)
!DEC$ ATTRIBUTES DECORATE, ALIAS:'fsubr' :: FSUBR
...
CHARACTER*(*) STRNG
...

Using the default calling convention for the Fortran code and __cdecl for the C code I end up with STRNG having an undefined address when I step into the Fortran routine.

Regards, Mike