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From: bryce@hoser.berkeley.edu (Bryce Nesbitt)
Newsgroups: comp.sys.amiga
Subject: Re: Dynamic Stack Allocation
Message-ID: <21440@ucbvax.BERKELEY.EDU>
Date: Sun, 25-Oct-87 20:18:43 EST
Article-I.D.: ucbvax.21440
Posted: Sun Oct 25 20:18:43 1987
Date-Received: Tue, 27-Oct-87 06:04:44 EST
References: <4585@zen.berkeley.edu>
Sender: usenet@ucbvax.BERKELEY.EDU
Organization: University of California at Berkeley
Lines: 33
Summary: Here is how to check how large your stack is.

In article <4585@zen.berkeley.edu> c164-1bj@cordelia.berkeley.edu (Jonathan Dubman) writes:
>I have a speedy maze program I wrote in C that I want to send to Fred and post
>here, but it needs a large stack.  Maximum resolution requires about 150K of
>stack space. (Massive recursion.)  I don't want everybody who runs it without
>reading the docs first to crash their machine.
>
>Is it possible in a C program to know how much stack space I have?  I
>can write a short assembly language program if necessary.

From C, simply get a pointer to your task with "FindTask(0L);" This returns
a pointer to struct Task from the exec/tasks.h include file.  tc_SPLower is
the lower bound of the stack tc_SPupper is the upper bound +2.

It would be thoretically possible to allocate a new stack and start to use
it.  This sounds somewhat dangerous, however.  There is no official function
set up to swap stacks (and the requisite Task structure fields).  In the
future, particuarly the resource tracked future, you could be asking for
problems.  At least you know it is safe to:

>say, "Reset your stack size and run me again.".

Anyone starting it from Workbench will only get that message if they played
with the icon.  Anyone starting from the CLI when an icon exists can probably
figure out how to type "stack 150000".

Sounds like your program should also leave the automatic stack checking code
in.  This will pop a "Stack overflow" requester if a function call will
overflow.  You *must*, however, catch the exit and do a proper cleanup.

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