[Info-vax] VMS port to x86

[glen herrmannsfeldt]

Bob Koehler <koehler at eisner.nospam.encompasserve.org> wrote:

(snip, I wrote)
>> To make that work, the linker fixes things up.

>   I've seen the linker on TOPS-20 do that.  But not on VMS.  The
>   TOPS-20 calling standard incudes sufficent flags in the high bits
>   of the address field to figure it out.  I'm not aware of anything
>   in the VMS object file that would allow the linker to figure it out.

>   Can you generate an example using a VMS Fortran compiler?

The example looks something like:

      CALL SUB1('wxyz')
      CALL SUB2('wxyz')
      STOP
      END
      SUBROUTINE SUB1(I)
      WRITE(6,1) I
1     FORMAT(A4)
      RETURN
      END
      SUBROUTINE SUB2(C)
      CHARACTER*4 C
      WRITE(6,1) C
1     FORMAT(A4)
      RETURN
      END

SUB1 needs a %REF, SUB2 needs a %descr.

>   I have not seen any compiler that would generate different calling
>   conventions depending on whether the CHARACTER data was a variable 
>   or a constant.

No, it depends on the callee, not the caller.

(snip)

>   TOPS-20, as a different example, had only a Fortran 66 compiler for a
>   long time and the system did need to be able to mix Fortran 66 and 77
>   character conventions.

Maybe it was done there first, and later VAX.

-- glen