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From: bds@mtgzz.UUCP (b.d.szablak)
Newsgroups: comp.sys.atari.st
Subject: TPA pointer
Message-ID: <3059@mtgzz.UUCP>
Date: Fri, 11-Sep-87 09:15:34 EDT
Article-I.D.: mtgzz.3059
Posted: Fri Sep 11 09:15:34 1987
Date-Received: Sat, 12-Sep-87 17:55:21 EDT
Organization: AT&T, Middletown NJ
Lines: 17
Keywords: bizarre behavior, entry points

I've observed strange things happening last night on my ST while working
on an assembly program. After spending some time tracking down a bug in
the program's bowels, I started finding my program dying (2 bombs) right
at startup. Expecting that the problem was caused by a previous crash
I powered down (not just a reset) and tried again with the same result. 

Using MONST I determined that the error was occurring because the value
I was using for the TPA pointer (passed on top of the stack at startup)
was 0L! I reassembled the program with a TRAP #0 as the first instruction
in order to step through the program; the trap was never hit (a later one
was though)! I gave up at this point, but it seems that TOS is not starting
the program at its entry point.

This morning I talked to a friend of mine, and he had seen this same
problem himself some time ago. In his case, it went away the next day
he started working on this. Has anyone else seen this problem, and does
anyone have an explanation?