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| <h3 class="section">18.3 Index Files Speed Up <span class="sc">gdb</span></h3> |
| |
| <p><a name="index-index-files-1021"></a><a name="index-g_t_0040samp_007b_002egdb_005findex_007d-section-1022"></a> |
| When <span class="sc">gdb</span> finds a symbol file, it scans the symbols in the |
| file in order to construct an internal symbol table. This lets most |
| <span class="sc">gdb</span> operations work quickly—at the cost of a delay early |
| on. For large programs, this delay can be quite lengthy, so |
| <span class="sc">gdb</span> provides a way to build an index, which speeds up |
| startup. |
| |
| <p>The index is stored as a section in the symbol file. <span class="sc">gdb</span> can |
| write the index to a file, then you can put it into the symbol file |
| using <samp><span class="command">objcopy</span></samp>. |
| |
| <p>To create an index file, use the <code>save gdb-index</code> command: |
| |
| <dl> |
| <dt><code>save gdb-index </code><var>directory</var><dd><a name="index-save-gdb_002dindex-1023"></a>Create an index file for each symbol file currently known by |
| <span class="sc">gdb</span>. Each file is named after its corresponding symbol file, |
| with ‘<samp><span class="samp">.gdb-index</span></samp>’ appended, and is written into the given |
| <var>directory</var>. |
| </dl> |
| |
| <p>Once you have created an index file you can merge it into your symbol |
| file, here named <samp><span class="file">symfile</span></samp>, using <samp><span class="command">objcopy</span></samp>: |
| |
| <pre class="smallexample"> $ objcopy --add-section .gdb_index=symfile.gdb-index \ |
| --set-section-flags .gdb_index=readonly symfile symfile |
| </pre> |
| <p>There are currently some limitation on indices. They only work when |
| for DWARF debugging information, not stabs. And, they do not |
| currently work for programs using Ada. |
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