1<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> 2<html> 3<!-- Copyright (C) 1988-2021 Free Software Foundation, Inc. 4 5Permission is granted to copy, distribute and/or modify this document 6under the terms of the GNU Free Documentation License, Version 1.3 or 7any later version published by the Free Software Foundation; with the 8Invariant Sections being "Free Software" and "Free Software Needs 9Free Documentation", with the Front-Cover Texts being "A GNU Manual," 10and with the Back-Cover Texts as in (a) below. 11 12(a) The FSF's Back-Cover Text is: "You are free to copy and modify 13this GNU Manual. 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It is common practice for vendors to start with 77a standard processor core — ARM, PowerPC, or <acronym>MIPS</acronym>, for example — 78and then make changes to adapt it to a particular market niche. Some 79architectures have hundreds of variants, available from dozens of 80vendors. This leads to a number of problems: 81</p> 82<ul> 83<li> With so many different customized processors, it is difficult for 84the <small>GDB</small> maintainers to keep up with the changes. 85</li><li> Since individual variants may have short lifetimes or limited 86audiences, it may not be worthwhile to carry information about every 87variant in the <small>GDB</small> source tree. 88</li><li> When <small>GDB</small> does support the architecture of the embedded system 89at hand, the task of finding the correct architecture name to give the 90<code>set architecture</code> command can be error-prone. 91</li></ul> 92 93<p>To address these problems, the <small>GDB</small> remote protocol allows a 94target system to not only identify itself to <small>GDB</small>, but to 95actually describe its own features. This lets <small>GDB</small> support 96processor variants it has never seen before — to the extent that the 97descriptions are accurate, and that <small>GDB</small> understands them. 98</p> 99<p><small>GDB</small> must be linked with the Expat library to support XML 100target descriptions. See <a href="Requirements.html#Expat">Expat</a>. 101</p> 102<table class="menu" border="0" cellspacing="0"> 103<tr><td align="left" valign="top">• <a href="Retrieving-Descriptions.html#Retrieving-Descriptions" accesskey="1">Retrieving Descriptions</a>:</td><td> </td><td align="left" valign="top">How descriptions are fetched from a target. 104</td></tr> 105<tr><td align="left" valign="top">• <a href="Target-Description-Format.html#Target-Description-Format" accesskey="2">Target Description Format</a>:</td><td> </td><td align="left" valign="top">The contents of a target description. 106</td></tr> 107<tr><td align="left" valign="top">• <a href="Predefined-Target-Types.html#Predefined-Target-Types" accesskey="3">Predefined Target Types</a>:</td><td> </td><td align="left" valign="top">Standard types available for target 108 descriptions. 109</td></tr> 110<tr><td align="left" valign="top">• <a href="Enum-Target-Types.html#Enum-Target-Types" accesskey="4">Enum Target Types</a>:</td><td> </td><td align="left" valign="top">How to define enum target types. 111</td></tr> 112<tr><td align="left" valign="top">• <a href="Standard-Target-Features.html#Standard-Target-Features" accesskey="5">Standard Target Features</a>:</td><td> </td><td align="left" valign="top">Features <small>GDB</small> knows about. 113</td></tr> 114</table> 115 116<hr> 117<div class="header"> 118<p> 119Next: <a href="Operating-System-Information.html#Operating-System-Information" accesskey="n" rel="next">Operating System Information</a>, Previous: <a href="Agent-Expressions.html#Agent-Expressions" accesskey="p" rel="previous">Agent Expressions</a>, Up: <a href="index.html#Top" accesskey="u" rel="up">Top</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p> 120</div> 121 122 123 124</body> 125</html> 126