[Info-vax] Technical issues with VMS BASIC port to x86-64 ?

[Dave Froble]

On 2/20/2024 6:44 PM, Arne Vajhøj wrote:
> On 2/20/2024 5:28 PM, Lawrence D'Oliveiro wrote:
>> On Tue, 20 Feb 2024 15:33:15 -0500, Arne Vajhøj wrote:
>
> (technically Id did not write that - I quoted John)
>
>>> (I can really bore you on overlaid PSECTs on OpenVMS vs .comm directives
>>> in UNIX)
>>
>> Is it a namespace issue? Because .comm names live in the same namespace as
>> global symbol names?
>
> There are probably multiple differences.
>
> And a lot of code triggering the problems are probably rather bad code.
> But the expectation for VMS x86-64 is 99.9999% compatibility not 99%
> compatibility.
>
> If I remember correctly then the example given in one of these threads
> were a Fortran common block where some part of the data was initialized
> in some code and other part of the data was initialized in other code.
>
> Arne
>
>

Back in Basic+ there was/is the FIELD operator.  It was/is used to dynamically 
assign label(s) to locations in an I/O buffer.  For example,

FIELD #1%, 2 as Z1$, 8 as Z2$, 20 as Z3$

The variables then had their descriptors modified to have addresses in the I/O 
buffer associated with channel #1.  After all, what good is I/O unless one can 
access the data?

The VAX Basic people really didn't like the operator and the concept.  They 
wanted to have RMS in move mode move a record into a MAP that was NOT accessing 
the I/O buffer.

Didn't sit too well with those coming from RSTS.  Their (VAX BASIC) response was 
the dynamic map capabilities.  What they did to achieve this, I don't know. 
Maybe that is where the weirdness comes from.

We didn't use their dynamic MAP capabilities.  We were rather happy with working 
in the I/O buffer, and developed software to re-purpose string variables as 
labels in an I/O buffer.  Seemed reasonable to us.  Image rundown got rather 
upset if the string descriptors were not returned to their initial state.

:-)

-- 
David Froble                       Tel: 724-529-0450
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