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From: Schauble@MIT-MULTICS.ARPA.UUCP
Newsgroups: mod.computers.vax
Subject: Null arguments in VMS Fortran
Message-ID: <870105082506.589990@MIT-MULTICS.ARPA>
Date: Mon, 5-Jan-87 03:25:00 EST
Article-I.D.: MIT-MULT.870105082506.589990
Posted: Mon Jan  5 03:25:00 1987
Date-Received: Mon, 5-Jan-87 05:35:50 EST
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The ARPA Internet
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Approved: info-vax@sri-kl.arpa

My previous question about null arguments produced two replies to the
effect that, yes, the subroutine can be written in Fortran. They
proposed something like

        CALL SUBB(X,,Y)

        subroutine subb(a,b,c)
        ...
        v = default
        if (%loc(b).ne.0) v = b

Assume that this is the only reference to b in the subroutine.

This looks good except for one small problem. Several compilers that I
have dealt with that use a similar linkage convention will generate a
preamble that will move read-only formal parameters into the
subroutine's local data space. Further references can be done faster
than the indirect reference usually needed for a parameter.

I know that VMS Fortran has a very good optimizer. Does it really not do
this optimization? And does the above really work?

          Thanks,
          Paul <Schauble at MIT-Multics>