[Info-vax] How much of VMS is still in MACRO-32?

[Arne Vajhøj]

On 5/31/2021 4:26 PM, Stephen Hoffman wrote:
> On 2021-05-31 13:07:28 +0000, Simon Clubley said:
>> Is there any self-modifying code in VMS ? (I hope the answer to that 
>> is no, BTW. :-))
> 
> There's DCL around that is self-modifying. Which is part of why 
> compiling DCL can be such "fun".
> 
> I'm not aware of self-modifying code or a JIT within OpenVMS itself, 
> though I'm a little murky on the full "creativitity" of the debugger in 
> this context.
> 
> There is some related support present (INSTRUCTION_MB, EVAX_IMB, etc) 
> which certainly implies self-modifying code does exist.
> 
> I've written and have met self-modifying app code for OpenVMS.  As have 
> others. Including Oracle Rdb, IIRC.
> 
> Met some app code that invoked a compiler and linker and then FIS'd that 
> code into the app, too. That was clunky and very limited, but workable 
> for that app.
> 
> There's Java and its JIT, of course.

It may be relevant to distinguish between:
A) dynamic code generation where an application generate
    new code and execute it
B) code that modifies itself aka replace some of its code
    with new code

#A probably have more legitimate uses than #B.

Arne