Re: A86:New in town "stack pointers"

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Re: A86:New in town "stack pointers"


this method:
    ld hl,(_OPBASE)
    push hl
    ld hl,(_FPBASE)
    push hl
    ld hl,(_OPS)
    ld (_OPBASE),hl
    ld hl,(_FPS)
    ld (_FPBASE),hl
    call _exec_basic
    pop hl
    ld (_FPBASE),hl
    pop hl
    ld (_OPBASE),hl
gives an "undefined" error on the last line of the basic program if stop
gets executed. 

if you replace the call to _exec_basic (aka _PLOTPARS) with this:
    ld hl,error_h
    call _insterr ;_pushErrorHandler = $41a1
    call _exec_basic
    call _removerr ;_popErrorHandler = $41a4
error_h:
all errors, including that one will be ignored.

-josh

On Mon, 21 Feb 2000 19:53:43 -0700 "Kirk Meyer" <kirkmeyer@bigfoot.com>
writes:
> 
> Haha, we went through this before! It was already suggested to 
> modify the
> stack pointers. Apparently no one bothered to try it. (It is 
> possible that
> you might run into other hidden problems even after fixing this, but
> doubtful.) For shells, however, the BASIC loader approach is usually 
> the
> best anyway, since you'll want them to be able to run the shell 
> simply and
> not with Asm(. The approach of replacing the Stop token and 
> installing an
> error handler sounds interesting, but seems a bit too hackish to 
> work with
> out a WHOLE lot of effort. Seems to me the easiest route is to 
> tinker with
> the stacks...
> 
> ----- Original Message -----
> From: David Phillips <david@acz.org>
> To: <assembly-86@lists.ticalc.org>
> Sent: Monday, February 21, 2000 6:45 PM
> Subject: Re: A86:New in town
> 
> 
> > The problem is with the stack.  'stop' is sort of like 
> _jforcecmdnochar in
> > assembly, or how you would do it by hand.  Nuke the stack and 
> exit.  But
> > since you are calling it from an assembly program, and they didn't 
> store
> the
> > correct info in ram to return to the assembly program, it screws 
> up.
> >
> > Hmm...it just might be possible to go through and replace the 
> token for
> > 'stop' with something that would cause an error.  And if you 
> installed an
> > error handler before you ran the program...
> 
> 
> 

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