Mercurial > hg > index.cgi

view docs/manual/c13.html @ 434:052c5f335a92

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
Fix bug in like terms collection in expression simplification Like term collection would lose the actual "variable" part of the term if the second term collected happened to have no coefficient. This would cause the expression to take the value of the calculated coefficient which is obviously wrong. Thanks to hider <stego@satx.rr.com> for reporting the bug and providing a proper test case. Observation: this bug has been present since the first pre-release of lwtools 3.0 when the algebraic expression system was introduced. Apparently people tend not to create expressions that trigger the like terms handler. The specific conditions require the symbol to be undefined and the second operand to the addition has to have no coefficient so it's likely a fairly rare scenario. Still, it is somewhat surprising that nobody tripped on it before now.
author William Astle <lost@l-w.ca>
date Mon, 23 Jan 2017 22:58:36 -0700
parents b30091890d62
children
line wrap: on
line source

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN""http://www.w3.org/TR/html4/loose.dtd">
<HTML
><HEAD
><TITLE
>Introduction</TITLE
><META
NAME="GENERATOR"
CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK
REL="HOME"
TITLE="LW Tool Chain"
HREF="index.html"><LINK
REL="PREVIOUS"
TITLE="LW Tool Chain"
HREF="index.html"><LINK
REL="NEXT"
TITLE="Output Formats"
HREF="c21.html"></HEAD
><BODY
CLASS="CHAPTER"
BGCOLOR="#FFFFFF"
TEXT="#000000"
LINK="#0000FF"
VLINK="#840084"
ALINK="#0000FF"
><DIV
CLASS="NAVHEADER"
><TABLE
SUMMARY="Header navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TH
COLSPAN="3"
ALIGN="center"
>LW Tool Chain</TH
></TR
><TR
><TD
WIDTH="10%"
ALIGN="left"
VALIGN="bottom"
><A
HREF="index.html"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="80%"
ALIGN="center"
VALIGN="bottom"
></TD
><TD
WIDTH="10%"
ALIGN="right"
VALIGN="bottom"
><A
HREF="c21.html"
ACCESSKEY="N"
>Next</A
></TD
></TR
></TABLE
><HR
ALIGN="LEFT"
WIDTH="100%"></DIV
><DIV
CLASS="CHAPTER"
><H1
><A
NAME="AEN13"
></A
>Chapter 1. Introduction</H1
><P
>The LW tool chain provides utilities for building binaries for MC6809 and
HD6309 CPUs. The tool chain includes a cross-assembler and a cross-linker
which support several styles of output.</P
><DIV
CLASS="SECTION"
><H1
CLASS="SECTION"
><A
NAME="AEN16"
>1.1. History</A
></H1
><P
>For a long time, I have had an interest in creating an operating system for
the Coco3. I finally started working on that project around the beginning of
2006. I had a number of assemblers I could choose from. Eventually, I settled
on one and started tinkering. After a while, I realized that assembler was not
going to be sufficient due to lack of macros and issues with forward references.
Then I tried another which handled forward references correctly but still did
not support macros. I looked around at other assemblers and they all lacked
one feature or another that I really wanted for creating my operating system.</P
><P
>The solution seemed clear at that point. I am a fair programmer so I figured
I could write an assembler that would do everything I wanted an assembler to
do. Thus the LWASM probject was born. After more than two years of on and off
work, version 1.0 of LWASM was released in October of 2008.</P
><P
>As the aforementioned operating system project progressed further, it became
clear that while assembling the whole project through a single file was doable,
it was not practical. When I found myself playing some fancy games with macros
in a bid to simulate sections, I realized I needed a means of assembling
source files separately and linking them later. This spawned a major development
effort to add an object file support to LWASM. It also spawned the LWLINK
project to provide a means to actually link the files.</P
></DIV
></DIV
><DIV
CLASS="NAVFOOTER"
><HR
ALIGN="LEFT"
WIDTH="100%"><TABLE
SUMMARY="Footer navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
><A
HREF="index.html"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="index.html"
ACCESSKEY="H"
>Home</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
><A
HREF="c21.html"
ACCESSKEY="N"
>Next</A
></TD
></TR
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
>LW Tool Chain</TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
>&nbsp;</TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
>Output Formats</TD
></TR
></TABLE
></DIV
></BODY
></HTML
>