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From: dxf <dxforth@gmail.com>
Newsgroups: comp.lang.forth
Subject: Re: PAD and preemptive multi-tasking
Date: Sat, 21 Dec 2024 10:49:48 +1100
Organization: i2pn2 (i2pn.org)
Message-ID: <bb67ecf90c16a2038a7d366cfa35a07a671c2b58@i2pn2.org>
References: <2024Dec20.111031@mips.complang.tuwien.ac.at>
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On 20/12/2024 9:10 pm, Anton Ertl wrote:
> Bernd Paysan have been wondering what to do about PAD in the presence
> of preemptive multitasking (but not multi-user) as implemented in
> Gforth.

You may need to explain 'preemptive' and its relevance here.

> We see two possible scenarios:
> 
> If PAD is used only directly by the user for interactive work, only
> one PAD is needed.
> 
> OTOH, if PAD is used as temporary storage in words that may be called
> by any task, PAD needs to be part of the per-task (aka USER) data.
> 
> My understanding is that classical multi-tasking Forth systems
> (polyForth, I guess) were also multi-user and had one dictionary per
> task, so they also had one dictionary pointer and therefore one PAD
> per task, but I have not worked with any of them and the descriptions
> I have read have been very sketchy, so this could be wrong.

Based on a part disassembly the value of HERE (used as DP) was taken
from the user area and PAD was 34 bytes above that value.

> In any case, the question is how PAD is used by current programs that
> might be run on Gforth.
> 
> - anton