[Info-vax] VMS internals design, was: Re: BASIC and AST routines

[Simon Clubley]

On 2021-11-25, VAXman-  @SendSpamHere.ORG <VAXman- at SendSpamHere.ORG> wrote:
>
> Trolling and changing the thread subject line does not excuse you from
> answering the question I asked.  <crickets... in November nonetheless>
>
> Troll, troll troll, the troll is marching...
>

I already answered your question Brian as you would have seen if you
had actually read my replies.

It turns out that the reason those arguments are available to the called
function is because VMS needs to preserve those registers across the AST
call and some bright spark during the design of VMS thought it was
acceptable to push those registers onto a user-visible call frame instead
of storing them in a private area that the called AST function did not
have access to.

That's the kind of design decision that was so insane it should never
have passed a design review but at least it appears to have been fixed
in later architectures with a private storage area, just like it should
have been on VAX.

And the reason I thought it _must_ be Macro-32 related was because the
real reason was so crazy it never even occurred to me. :-)

Simon.

-- 
Simon Clubley, clubley at remove_me.eisner.decus.org-Earth.UFP
Walking destinations on a map are further away than they appear.