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

[Bob Gezelter]

On Wednesday, December 1, 2021 at 3:46:00 PM UTC-5, Arne Vajhøj wrote:
> 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
Arne,

I know this problem.  Encountered it at a client. 

BASIC checks the parameter count. Done. C and others do not .

- Bob Gezelter, http://www.rlgsc.com