Mercurial > hg > index.cgi

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN""http://www.w3.org/TR/html4/loose.dtd">
<HTML
><HEAD
><TITLE
>Linker Operation</TITLE
><META
NAME="GENERATOR"
CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK
REL="HOME"
TITLE="LW Tool Chain"
HREF="index.html"><LINK
REL="UP"
TITLE="LWLINK"
HREF="c662.html"><LINK
REL="PREVIOUS"
TITLE="LWLINK"
HREF="c662.html"><LINK
REL="NEXT"
TITLE="Linking Scripts"
HREF="x776.html"></HEAD
><BODY
CLASS="SECTION"
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="c662.html"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="80%"
ALIGN="center"
VALIGN="bottom"
>Chapter 4. LWLINK</TD
><TD
WIDTH="10%"
ALIGN="right"
VALIGN="bottom"
><A
HREF="x776.html"
ACCESSKEY="N"
>Next</A
></TD
></TR
></TABLE
><HR
ALIGN="LEFT"
WIDTH="100%"></DIV
><DIV
CLASS="SECTION"
><H1
CLASS="SECTION"
><A
NAME="AEN762"
>4.2. Linker Operation</A
></H1
><P
>&#13;LWLINK takes one or more files in supported input formats and links them
into a single binary. Currently supported formats are the LWTOOLS object
file format and the archive format used by LWAR. While the precise method is
slightly different, linking can be conceptualized as the following steps.&#13;</P
><P
></P
><OL
TYPE="1"
><LI
><P
>First, the linker loads a linking script. If no script is specified, it
loads a built-in default script based on the output format selected. This
script tells the linker how to lay out the various sections in the final
binary.</P
></LI
><LI
><P
>Next, the linker reads all the input files into memory. At this time, it
flags any format errors in those files. It constructs a table of symbols
for each object at this time.</P
></LI
><LI
><P
>The linker then proceeds with organizing the sections loaded from each file
according to the linking script. As it does so, it is able to assign addresses
to each symbol defined in each object file. At this time, the linker may
also collapse different instances of the same section name into a single
section by appending the data from each subsequent instance of the section
to the first instance of the section.</P
></LI
><LI
><P
>Next, the linker looks through every object file for every incomplete reference.
It then attempts to fully resolve that reference. If it cannot do so, it
throws an error. Once a reference is resolved, the value is placed into
the binary code at the specified section. It should be noted that an
incomplete reference can reference either a symbol internal to the object
file or an external symbol which is in the export list of another object
file.</P
></LI
><LI
><P
>If all of the above steps are successful, the linker opens the output file
and actually constructs the binary.</P
></LI
></OL
></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="c662.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="x776.html"
ACCESSKEY="N"
>Next</A
></TD
></TR
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
>LWLINK</TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="c662.html"
ACCESSKEY="U"
>Up</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
>Linking Scripts</TD
></TR
></TABLE
></DIV
></BODY
></HTML
>
author	William Astle <lost@l-w.ca>
date	Sun, 10 Jun 2012 14:14:43 -0600
parents	1e0a0e6cd918
children