Message-ID:	<8D53104ECD0CD211AF4000A0C9D60AE335BE25@probe-2.Acclaim-Euro.net>
From:	Shawn Hargreaves <ShawnH AT Probe DOT co DOT uk>
To:	Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>
Cc:	djgpp AT delorie DOT com
Subject:	RE: how to switch tasks?
Date:	Thu, 17 Dec 1998 15:20:04 -0000
MIME-Version:	1.0
X-Mailer:	Internet Mail Service (5.0.1460.8)
Reply-To:	djgpp AT delorie DOT com

> Eli Zaretskii writes:
>> I think you can do it by using the signal handling mechanism to defer 
>> the event into a protected mode exception, and then using setjmp() / 
>> longjmp().
>
> True, but the original poster wanted to use task-switching to emulate 
> things like fork(), and that's not possible with signals, since once you 
> spawn another pogram, you are parked inside a real-mode DOS call, and all 
> signals are effectively disabled until the child program exits.

A good point: I missed that part of the discussion. You could still 
implement a signal-based version of fork() when spawning a djgpp 
program from another djgpp application, since that can be done 
without ever bothering to invoke DOS, but this is quite a hairy 
assumption to make, and a big restriction on when the method could 
be used...


	Shawn Hargreaves.

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