Re: A86: Re: calling and returning

To: assembly-86@lists.ticalc.org
Subject: Re: A86: Re: calling and returning
From: ComAsYuAre@aol.com
Date: Sun, 5 Dec 1999 22:40:03 EST
Reply-To: assembly-86@lists.ticalc.org


If you want to save the sp, there is a much shorter/easier way to do it:

;at the beginning of the program
  ld (StackSave),sp


;and later in the code
  ld sp,0
StackSave = $-2
  ret


In a message dated 12/5/99 20:39:23 Eastern Standard Time, david@acz.org 
writes:

> Actually, there's another way, and that is to store the stack location when
>  the program starts:
>  
>  StackSave = ...      ; somewhere free in ram, like _textShadow or something
>  
>   ld hl,0
>   add hl,sp                    ; HL = SP
>   ld (StackSave),hl        ; ah, I miss 16 bit loads...
>  
>  ...
>  
>  ReturnToOSNoMatterWhereWeAre:
>   ld hl,(StackSave)         ; get the stack pointer back
>   ld sp,hl                        ; restore the stack pointer
>   ret                               ; back to the OS!!!



----
Jonah Cohen
<ComAsYuAre@aol.com>
http://linux.hypnotic.org/~jonah/

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