[Info-vax] BASIC and AST routines

[Simon Clubley]

On 2021-11-23, VAXman-  @SendSpamHere.ORG <VAXman- at SendSpamHere.ORG> wrote:
> In article <snjcd1$9hn$2 at dont-email.me>, Simon Clubley <clubley at remove_me.eisner.decus.org-Earth.UFP> writes:
>>
>>That VMS API passes in a stack pointer, a PC and what were originally
>>two architecture-specific registers.
>
> That doesn't answer your aspersions WRT Macro-32.  Try, do try again.
> I'll be waiting. Also, please tell me about this stack pointer you've
> now claimed to be passed along too.
>

You are correct Brian. I wrongly thought it was the SP for some reason
instead of the PS/PSL. However, passing an architecture-specific PS/PSL
register to the AST is even more ridiculous than passing the SP.

>
>
>>That kind of information simply would not be exposed at application
>>code level in a modern version of that API as it would (rightly) be
>>treated as an implementation specific detail that would be handled
>>by the compiler.
>
> Oh, please explain then how are ASTs handled in *ix?  <LOL>
>

Here is one example of how asynchronous callbacks are handled in Linux:

https://linux.die.net/man/3/dlm_lock

For a proper hardware-level callback when code is written in C, looking
at microcontroller interrupt handlers would be a good example.

In that world, you can either tag the interrupt handler with an __ISR
attribute and let the compiler generate the correct code for you, or
the underlying OS environment can wrap calls to the C language interrupt
handler with an assembly language handler that is utterly invisible to
the C language interrupt handler itself.

Here is how one compiler for the PIC32MX (a MIPS MCU) handles this:

https://microchipdeveloper.com/32bit:mx-arch-exceptions-usage

>
>
>>That information is only needed because the lowest supported application
>>language on VMS is Macro-32 and not C (or another comparable low-level
>>language).
>
> You're slinging your BULLSHIT yet again.  Macro-32 has no inherent need
> or want to know R0, R1, the PC at AST delivery or the PS/PSL.  As I have
> requested previously, if you want to be slinging manure in here, please
> show us your shovel.
>

Fine. So why are these architecture-specific registers passed to what
is essentially a callback function in a normal application program
and why do those registers need to be visible from that same callback
function ?

Simon.

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