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

[Arne Vajhøj]

On 12/1/2021 3:35 PM, Dave Froble wrote:
> Ok, got a bit un-lazy, tried it.
> 
> This works:
> 
> 1       !************************************************
>          !     Timer AST Timeout Handler to Cancel I/O
>          !************************************************
> 
>          SUB TCP_TIMER(  LONG CH% , &
>                          LONG Z2% , &
>                          LONG Z3% , &
>                          LONG Z4% , &
>                          LONG Z5% )
> 
>          CALL SYS$CANCEL( Loc(CH%) By Value )
> 
>          SubEnd
> 
> This does not work:
> 
> 1       !************************************************
>          !     Timer AST Timeout Handler to Cancel I/O
>          !************************************************
> 
>          SUB TCP_TIMER(  LONG CH% )
> 
>          CALL SYS$CANCEL( Loc(CH%) By Value )
> 
>          SubEnd
> 
> It seems to have a problem when issuing a read on an I/O channel, not 
> when invoking the QIO that specifies the AST routine.
> 
> I'm not complaining, this was just a test.  I'm a bit curious what 
> caused the error, there was no evident error code or such.
> 
> In the debugger, there was a report of "too many arguments" or something 
> like that.  I'm just guessing that at some point Basic caused some count 
> of arguments and decided that there were too many arguments for the 
> routine as declared.
> 
> I hate it when the computer thinks it's smarter than me.  Of course that 
> bar isn't too high.
> 
> :-)

Basic is different from some more low level languages.

But I don't see a problem with Basic here.

The AST function is being called with 5 arguments and
the AST function is declared to receive 1 argument, so
something in the generated code does not like it.

Seems perfectly fair to me.

Obviously the documentation should be very clear
about the 5 arguments.

Arne