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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 | fc166b3bbae3 |
children | cad5937314cb |
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN""http://www.w3.org/TR/html4/loose.dtd"> <HTML ><HEAD ><TITLE >LW Tool Chain</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK REL="NEXT" TITLE="Introduction" HREF="c13.html"></HEAD ><BODY CLASS="BOOK" BGCOLOR="#FFFFFF" TEXT="#000000" LINK="#0000FF" VLINK="#840084" ALINK="#0000FF" ><DIV CLASS="BOOK" ><A NAME="AEN1" ></A ><DIV CLASS="TITLEPAGE" ><H1 CLASS="TITLE" ><A NAME="AEN2" >LW Tool Chain</A ></H1 ><H3 CLASS="AUTHOR" ><A NAME="AEN4" ></A >William Astle</H3 ><H3 CLASS="AUTHOR" ><A NAME="AEN7" ></A >LWTools Contributors </H3 ><P CLASS="COPYRIGHT" >Copyright © 2009-2015 William Astle and LWTools contributors</P ><HR></DIV ><DIV CLASS="TOC" ><DL ><DT ><B >Table of Contents</B ></DT ><DT >1. <A HREF="c13.html" >Introduction</A ></DT ><DD ><DL ><DT >1.1. <A HREF="c13.html#AEN16" >History</A ></DT ></DL ></DD ><DT >2. <A HREF="c21.html" >Output Formats</A ></DT ><DD ><DL ><DT >2.1. <A HREF="c21.html#AEN24" >Raw Binaries</A ></DT ><DT >2.2. <A HREF="x27.html" >DECB Binaries</A ></DT ><DT >2.3. <A HREF="x32.html" >ASCII Hexadecimal</A ></DT ><DT >2.4. <A HREF="x36.html" >Motorola S-Record</A ></DT ><DT >2.5. <A HREF="x41.html" >Intel Hex</A ></DT ><DT >2.6. <A HREF="x46.html" >OS9 Modules</A ></DT ><DT >2.7. <A HREF="x54.html" >Object Files</A ></DT ></DL ></DD ><DT >3. <A HREF="c62.html" >LWASM</A ></DT ><DD ><DL ><DT >3.1. <A HREF="c62.html#AEN65" >Command Line Options</A ></DT ><DT >3.2. <A HREF="x218.html" >Dialects</A ></DT ><DT >3.3. <A HREF="x227.html" >Source Format</A ></DT ><DT >3.4. <A HREF="x237.html" >Symbols</A ></DT ><DT >3.5. <A HREF="x242.html" >Numbers and Expressions</A ></DT ><DT >3.6. <A HREF="x250.html" >Assembler Directives</A ></DT ><DD ><DL ><DT >3.6.1. <A HREF="x250.html#AEN253" >Data Directives</A ></DT ><DT >3.6.2. <A HREF="x250.html#AEN364" >Address Definition</A ></DT ><DT >3.6.3. <A HREF="x250.html#AEN415" >Conditional Assembly</A ></DT ><DT >3.6.4. <A HREF="x250.html#AEN486" >OS9 Target Directives</A ></DT ><DT >3.6.5. <A HREF="x250.html#AEN511" >Miscelaneous Directives</A ></DT ></DL ></DD ><DT >3.7. <A HREF="x551.html" >Macros</A ></DT ><DT >3.8. <A HREF="x574.html" >Structures</A ></DT ><DT >3.9. <A HREF="x595.html" >Object Files and Sections</A ></DT ><DT >3.10. <A HREF="x659.html" >Assembler Modes and Pragmas</A ></DT ><DT >3.11. <A HREF="x795.html" >Convenience Instructions</A ></DT ><DT >3.12. <A HREF="x800.html" >Cycle Counts</A ></DT ></DL ></DD ><DT >4. <A HREF="c806.html" >LWLINK</A ></DT ><DD ><DL ><DT >4.1. <A HREF="c806.html#AEN809" >Command Line Options</A ></DT ><DT >4.2. <A HREF="x906.html" >Linker Operation</A ></DT ><DT >4.3. <A HREF="x920.html" >Linking Scripts</A ></DT ><DT >4.4. <A HREF="x986.html" >Format Specific Linking Notes</A ></DT ><DD ><DL ><DT >4.4.1. <A HREF="x986.html#AEN989" >OS9 Modules</A ></DT ></DL ></DD ></DL ></DD ><DT >5. <A HREF="c1001.html" >Libraries and LWAR</A ></DT ><DD ><DL ><DT >5.1. <A HREF="c1001.html#AEN1005" >Command Line Options</A ></DT ></DL ></DD ><DT >6. <A HREF="c1063.html" >Object Files</A ></DT ></DL ></DIV ><DIV CLASS="LOT" ><DL CLASS="LOT" ><DT ><B >List of Tables</B ></DT ><DT >6-1. <A HREF="c1063.html#AEN1088" >Object File Term Types</A ></DT ><DT >6-2. <A HREF="c1063.html#AEN1118" >Object File Operator Numbers</A ></DT ></DL ></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" > </TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" > </TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="c13.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" > </TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" > </TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >Introduction</TD ></TR ></TABLE ></DIV ></BODY ></HTML >