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| <h3 class="section">7.2 Transformations on Symbol Tables</h3> |
| |
| <p>The linker concatenates object files and does fixups of externally |
| defined symbols. |
| |
| <p>You can see the transformations made on stab data by the assembler and |
| linker by examining the symbol table after each pass of the build. To |
| do this, use ‘<samp><span class="samp">nm -ap</span></samp>’, which dumps the symbol table, including |
| debugging information, unsorted. For stab entries the columns are: |
| <var>value</var>, <var>other</var>, <var>desc</var>, <var>type</var>, <var>string</var>. For |
| assembler and linker symbols, the columns are: <var>value</var>, <var>type</var>, |
| <var>string</var>. |
| |
| <p>The low 5 bits of the stab type tell the linker how to relocate the |
| value of the stab. Thus for stab types like <code>N_RSYM</code> and |
| <code>N_LSYM</code>, where the value is an offset or a register number, the |
| low 5 bits are <code>N_ABS</code>, which tells the linker not to relocate the |
| value. |
| |
| <p>Where the value of a stab contains an assembly language label, |
| it is transformed by each build step. The assembler turns it into a |
| relocatable address and the linker turns it into an absolute address. |
| |
| <ul class="menu"> |
| <li><a accesskey="1" href="Transformations-On-Static-Variables.html#Transformations-On-Static-Variables">Transformations On Static Variables</a> |
| <li><a accesskey="2" href="Transformations-On-Global-Variables.html#Transformations-On-Global-Variables">Transformations On Global Variables</a> |
| <li><a accesskey="3" href="Stab-Section-Transformations.html#Stab-Section-Transformations">Stab Section Transformations</a>: For some object file formats, |
| things are a bit different. |
| </ul> |
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