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| <title>Using as: Symbol Value</title> |
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| Next: <a href="Symbol-Type.html#Symbol-Type" accesskey="n" rel="next">Symbol Type</a>, Up: <a href="Symbol-Attributes.html#Symbol-Attributes" accesskey="u" rel="up">Symbol Attributes</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="AS-Index.html#AS-Index" title="Index" rel="index">Index</a>]</p> |
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| <a name="Value"></a> |
| <h4 class="subsection">5.5.1 Value</h4> |
| |
| <a name="index-value-of-a-symbol"></a> |
| <a name="index-symbol-value"></a> |
| <p>The value of a symbol is (usually) 32 bits. For a symbol which labels a |
| location in the text, data, bss or absolute sections the value is the |
| number of addresses from the start of that section to the label. |
| Naturally for text, data and bss sections the value of a symbol changes |
| as <code>ld</code> changes section base addresses during linking. Absolute |
| symbols’ values do not change during linking: that is why they are |
| called absolute. |
| </p> |
| <p>The value of an undefined symbol is treated in a special way. If it is |
| 0 then the symbol is not defined in this assembler source file, and |
| <code>ld</code> tries to determine its value from other files linked into the |
| same program. You make this kind of symbol simply by mentioning a symbol |
| name without defining it. A non-zero value represents a <code>.comm</code> |
| common declaration. The value is how much common storage to reserve, in |
| bytes (addresses). The symbol refers to the first address of the |
| allocated storage. |
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