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<!-- Copyright (C) 2003 Red Hat, Inc. --> <!-- This material may be distributed only subject to the terms --> <!-- and conditions set forth in the Open Publication License, v1.0 --> <!-- or later (the latest version is presently available at --> <!-- http://www.opencontent.org/openpub/). --> <!-- Distribution of the work or derivative of the work in any --> <!-- standard (paper) book form is prohibited unless prior --> <!-- permission is obtained from the copyright holder. --> <HTML ><HEAD ><TITLE >Editing the Sources</TITLE ><meta name="MSSmartTagsPreventParsing" content="TRUE"> <META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+ "><LINK REL="HOME" TITLE="eCos User Guide" HREF="ecos-user-guide.html"><LINK REL="UP" TITLE="Manual Configuration" HREF="manual-configuration.html"><LINK REL="PREVIOUS" TITLE="Editing an eCos Savefile" HREF="editing-an-ecos-savefile.html"><LINK REL="NEXT" TITLE="Modifying the Memory Layout" HREF="modifying-the-memory-layout.html"></HEAD ><BODY CLASS="SECT1" 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" >eCos User Guide</TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="bottom" ><A HREF="editing-an-ecos-savefile.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" >Chapter 28. Manual Configuration</TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" ><A HREF="modifying-the-memory-layout.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><DIV CLASS="SECT1" ><H1 CLASS="SECT1" ><A NAME="EDITING-THE-SOURCES">Editing the Sources</H1 ><P >For many users, controlling the packages and manipulating the available configuration options will be sufficient to create an embedded operating system that meets the application's requirements. However, since <SPAN CLASS="PRODUCTNAME" >eCos</SPAN > is shipped entirely in source form, it is possible to go further when necessary: you can edit the <SPAN CLASS="PRODUCTNAME" >eCos</SPAN > sources themselves. This requires some understanding of the way the <SPAN CLASS="PRODUCTNAME" >eCos</SPAN > build system works. </P ><P >The most obvious place to edit the source code is directly in the component repository. For example, you could edit the file <TT CLASS="FILENAME" >kernel/<TT CLASS="REPLACEABLE" ><I ><version></I ></TT >/src/sync/mutex.cxx</TT > to change the way kernel mutexes work, or possibly just to add some extra diagnostics or assertions. Once the file has been edited, it is possible to invoke <B CLASS="COMMAND" >make</B > at the top level of the build tree and the target library will be rebuilt as required. A small optimization is possible: the build tree is largely a mirror of the component repository, so it too will contain a subdirectory <TT CLASS="FILENAME" >kernel/<TT CLASS="REPLACEABLE" ><I ><version></I ></TT ></TT >; if make is invoked in this directory then it will only check for changes to the kernel sources, which is a bit more efficient than checking for changes throughout the component repository. </P ><P >Editing a file in the component repository is fine if this tree is used for only one <SPAN CLASS="PRODUCTNAME" >eCos</SPAN > configuration. If the repository is used for several different configurations, however, and especially if it is shared by multiple users, then making what may be experimental changes to the master sources would be a bad idea. The build system provides an alternative. It is possible to make a copy of the file in the build tree, in other words copy <TT CLASS="FILENAME" >mutex.cxx</TT > from the <TT CLASS="FILENAME" >kernel/<TT CLASS="REPLACEABLE" ><I ><version></I ></TT >/src/sync</TT > directory in the component repository to <TT CLASS="FILENAME" >kernel/<TT CLASS="REPLACEABLE" ><I ><version></I ></TT >/src/sync</TT > in the build tree, and edit the file in the build tree. When <B CLASS="COMMAND" >make</B > is invoked it will pick up local copies of any of the sources in preference to the master versions in the component repository. Once you have finished modifying the <SPAN CLASS="PRODUCTNAME" >eCos</SPAN > sources you can install the final version back in the component repository. If the changes were temporary in nature and only served to aid the debugging process, then you can discard the modified version of the sources. </P ><P >The situation is slightly more complicated for the header files that a package may export, such as the C library’s <TT CLASS="FILENAME" >stdio.h</TT > header file, which can be found in the directory <TT CLASS="FILENAME" >language/c/libc/<TT CLASS="REPLACEABLE" ><I ><version></I ></TT >/include</TT >. If such a header file is changed, either directly in the component repository or after copying it to the build tree, then <B CLASS="COMMAND" >make</B > must be invoked at the top level of the build tree. In cases like this it is not safe to rebuild just the C library because other packages may depend on the contents of <TT CLASS="FILENAME" >stdio.h</TT >. </P ></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="editing-an-ecos-savefile.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="ecos-user-guide.html" ACCESSKEY="H" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="modifying-the-memory-layout.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >Editing an <SPAN CLASS="PRODUCTNAME" >eCos</SPAN > Savefile</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="manual-configuration.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >Modifying the Memory Layout</TD ></TR ></TABLE ></DIV ></BODY ></HTML >
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