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| <h2 class="appendix">Appendix G Target Descriptions</h2> |
| <a name="index-target-descriptions"></a> |
| |
| <p>One of the challenges of using <small>GDB</small> to debug embedded systems |
| is that there are so many minor variants of each processor |
| architecture in use. It is common practice for vendors to start with |
| a standard processor core — ARM, PowerPC, or <acronym>MIPS</acronym>, for example — |
| and then make changes to adapt it to a particular market niche. Some |
| architectures have hundreds of variants, available from dozens of |
| vendors. This leads to a number of problems: |
| </p> |
| <ul> |
| <li> With so many different customized processors, it is difficult for |
| the <small>GDB</small> maintainers to keep up with the changes. |
| </li><li> Since individual variants may have short lifetimes or limited |
| audiences, it may not be worthwhile to carry information about every |
| variant in the <small>GDB</small> source tree. |
| </li><li> When <small>GDB</small> does support the architecture of the embedded system |
| at hand, the task of finding the correct architecture name to give the |
| <code>set architecture</code> command can be error-prone. |
| </li></ul> |
| |
| <p>To address these problems, the <small>GDB</small> remote protocol allows a |
| target system to not only identify itself to <small>GDB</small>, but to |
| actually describe its own features. This lets <small>GDB</small> support |
| processor variants it has never seen before — to the extent that the |
| descriptions are accurate, and that <small>GDB</small> understands them. |
| </p> |
| <p><small>GDB</small> must be linked with the Expat library to support XML |
| target descriptions. See <a href="Requirements.html#Expat">Expat</a>. |
| </p> |
| <table class="menu" border="0" cellspacing="0"> |
| <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. |
| </td></tr> |
| <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. |
| </td></tr> |
| <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 |
| descriptions. |
| </td></tr> |
| <tr><td align="left" valign="top">• <a href="Standard-Target-Features.html#Standard-Target-Features" accesskey="4">Standard Target Features</a>:</td><td> </td><td align="left" valign="top">Features <small>GDB</small> knows about. |
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