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| <h5 class="subsubsection">3.6.4.3 Input Section for Common Symbols</h5> |
| |
| <p><a name="index-common-symbol-placement-406"></a><a name="index-uninitialized-data-placement-407"></a>A special notation is needed for common symbols, because in many object |
| file formats common symbols do not have a particular input section. The |
| linker treats common symbols as though they are in an input section |
| named ‘<samp><span class="samp">COMMON</span></samp>’. |
| |
| <p>You may use file names with the ‘<samp><span class="samp">COMMON</span></samp>’ section just as with any |
| other input sections. You can use this to place common symbols from a |
| particular input file in one section while common symbols from other |
| input files are placed in another section. |
| |
| <p>In most cases, common symbols in input files will be placed in the |
| ‘<samp><span class="samp">.bss</span></samp>’ section in the output file. For example: |
| <pre class="smallexample"> .bss { *(.bss) *(COMMON) } |
| </pre> |
| <p><a name="index-scommon-section-408"></a><a name="index-small-common-symbols-409"></a>Some object file formats have more than one type of common symbol. For |
| example, the MIPS ELF object file format distinguishes standard common |
| symbols and small common symbols. In this case, the linker will use a |
| different special section name for other types of common symbols. In |
| the case of MIPS ELF, the linker uses ‘<samp><span class="samp">COMMON</span></samp>’ for standard common |
| symbols and ‘<samp><span class="samp">.scommon</span></samp>’ for small common symbols. This permits you |
| to map the different types of common symbols into memory at different |
| locations. |
| |
| <p><a name="index-g_t_005bCOMMON_005d-410"></a>You will sometimes see ‘<samp><span class="samp">[COMMON]</span></samp>’ in old linker scripts. This |
| notation is now considered obsolete. It is equivalent to |
| ‘<samp><span class="samp">*(COMMON)</span></samp>’. |
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