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From: bj@cbmvax.commodore.com (Brian Jackson)
Newsgroups: comp.sys.amiga.programmer
Subject: Re: General questions regarding Tasks
Message-ID: <21914@cbmvax.commodore.com>
Date: 25 May 91 01:33:59 GMT
References: <1991May24.160440.374@m.cs.uiuc.edu> <1991May24.120133.31035@kuhub.cc.ukans.edu>
Reply-To: bj@cbmvax.commodore.com (Brian Jackson)
Organization: Commodore, West Chester, PA
Lines: 46

In article <1991May24.120133.31035@kuhub.cc.ukans.edu> markv@kuhub.cc.ukans.edu writes:
>In article <1991May24.160440.374@m.cs.uiuc.edu>, schwager@m.cs.uiuc.edu (Michael Schwager) writes:
>> 
>> Hi,
>> I'm looking for guidelines about using tasks within C programs.
>  ...

>>  What do I need to be careful of (besides changing system variables)?
>
>Don't call DOS!!!  This also means don't call things like
>OpenLibrary() unless you know the library is in memory.  Many DOS
>functions that used to let you get away with being a task in 1.3 will
>barf in 2.0.  So don't call DOS or only OpenXXX call that could
>require something to be loaded off the disk.  If you do need access to
>such devices or libs, have the parent open it first to load it, and
>hold it open, then when the child opens it, it will be in memory.

Yes, and don't call anything that might, in turn, call DOS.

Be aware that there are some libraries that want 'task-specific'
information and the above trick will be less than optimal in those
cases. :)   It's really better in this case to just create a new
Process instead. Under 1.3 this is a tad arcane (but not really that
hard) and under 2.0 it's cake.

>>  Also, can I pass variables to a Task, like this:
>>      CreateTask ("Name", 0, func3 (var0, var1, var2), BIGSTACK);

Ths easiest way to do this (for me, anyway :)) is to have the child
task create a Message Port for such things. That way, you can make up
your own data structure in the parent, create the task, fill in the
structure with the data that the child needs and then PutMsg() the
thing to the child. You pretty much have to do this anyway since there
needs to be some mechanism to tell the child "we're going away now."

>Mark Gooderum

Brian

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/ Brian Jackson  Software Engineer, Commodore-Amiga Inc.    GEnie: B.J. \
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