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| <h2 class="appendix">Appendix G Target Descriptions</h2> |
| |
| <p><a name="index-target-descriptions-3638"></a> |
| One of the challenges of using <span class="sc">gdb</span> 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: |
| |
| <ul> |
| <li>With so many different customized processors, it is difficult for |
| the <span class="sc">gdb</span> maintainers to keep up with the changes. |
| <li>Since individual variants may have short lifetimes or limited |
| audiences, it may not be worthwhile to carry information about every |
| variant in the <span class="sc">gdb</span> source tree. |
| <li>When <span class="sc">gdb</span> does support the architecture of the embedded system |
| at hand, the task of finding the correct architecture name to give the |
| <samp><span class="command">set architecture</span></samp> command can be error-prone. |
| </ul> |
| |
| <p>To address these problems, the <span class="sc">gdb</span> remote protocol allows a |
| target system to not only identify itself to <span class="sc">gdb</span>, but to |
| actually describe its own features. This lets <span class="sc">gdb</span> support |
| processor variants it has never seen before — to the extent that the |
| descriptions are accurate, and that <span class="sc">gdb</span> understands them. |
| |
| <p><span class="sc">gdb</span> must be linked with the Expat library to support XML |
| target descriptions. See <a href="Expat.html#Expat">Expat</a>. |
| |
| <ul class="menu"> |
| <li><a accesskey="1" href="Retrieving-Descriptions.html#Retrieving-Descriptions">Retrieving Descriptions</a>: How descriptions are fetched from a target. |
| <li><a accesskey="2" href="Target-Description-Format.html#Target-Description-Format">Target Description Format</a>: The contents of a target description. |
| <li><a accesskey="3" href="Predefined-Target-Types.html#Predefined-Target-Types">Predefined Target Types</a>: Standard types available for target |
| descriptions. |
| <li><a accesskey="4" href="Enum-Target-Types.html#Enum-Target-Types">Enum Target Types</a>: How to define enum target types. |
| <li><a accesskey="5" href="Standard-Target-Features.html#Standard-Target-Features">Standard Target Features</a>: Features <span class="sc">gdb</span> knows about. |
| </ul> |
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