Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!knuth!mjbtn!raider!elgamy!elg
From: elg@elgamy.RAIDERNET.COM (Eric Lee Green)
Newsgroups: comp.sys.amiga.advocacy
Subject: Re: 8-bit death
Message-ID: <00674275937@elgamy.RAIDERNET.COM>
Date: 15 May 91 02:52:17 GMT
References: <1991May13.224027.9132@NCoast.ORG> <3626.tnews@templar.actrix.gen.nz> <1991May12.181436.20304@NCoast.ORG> <3691.tnews@templar.actrix.gen.nz>
Organization: Eric's Amiga 2000 @ Home
Lines: 31

From article <1991May13.224027.9132@NCoast.ORG>, by allbery@NCoast.ORG (Brandon S. Allbery KF8NH):
> And using a non-interrupt entry point runs the risk of somebody accidentally
> typo'ing a #define and making every program in existence break as a result.

This is the second time I've seen this, and I don't understand it. First of
all, the Amiga doesn't have any "system call" entry points. It has shared
libraries, some of which are located on disk (e.g. the IEEE math
simulation libraries for machines without a math chip) and some of which
happen to be built-in to the ROM. The compilers generate calls to these
libraries by using base pointer and offset (i.e., a jump table starts at
the library base pointer). How could typo'ing a #define break every program
in existence? When all those programs already have the correct offsets into
the library jump table compiled into them? Oh, you mean if one of the OS
people accidently insert a function into the jump table in the wrong place?
But that'd be caught early in the test-debug cycle, long before the library
was released to the general public. And nobody types in #defines for these
offsets... they're automagically generated from the Commodore-supplied
library description files, or linked in via a Commodore-supplied stub code
library (amiga.lib). Not that it matters, anyhow. Even if you were using
direct offsets (like some of the assembly language folks like to do),
typo'ing would just mean that your program would crash (i.e., would call
the wrong function). It wouldn't make any other program break. They already
have those offsets compiled into them.

So tell me, what exactly do you mean by "typo'ing a define and making
every program in existence break"? Because I just don't see how it could
happen, on the Amiga.

--
Eric Lee Green   (318) 984-1820  P.O. Box 92191  Lafayette, LA 70509
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