| <html lang="en"> |
| <head> |
| <title>Symbol Value - Using as</title> |
| <meta http-equiv="Content-Type" content="text/html"> |
| <meta name="description" content="Using as"> |
| <meta name="generator" content="makeinfo 4.13"> |
| <link title="Top" rel="start" href="index.html#Top"> |
| <link rel="up" href="Symbol-Attributes.html#Symbol-Attributes" title="Symbol Attributes"> |
| <link rel="next" href="Symbol-Type.html#Symbol-Type" title="Symbol Type"> |
| <link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage"> |
| <!-- |
| This file documents the GNU Assembler "as". |
| |
| Copyright (C) 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, |
| 2000, 2001, 2002, 2006, 2007, 2008, 2009, 2010 Free Software Foundation, Inc. |
| |
| Permission is granted to copy, distribute and/or modify this document |
| under the terms of the GNU Free Documentation License, Version 1.3 |
| or any later version published by the Free Software Foundation; |
| with no Invariant Sections, with no Front-Cover Texts, and with no |
| Back-Cover Texts. A copy of the license is included in the |
| section entitled ``GNU Free Documentation License''. |
| |
| --> |
| <meta http-equiv="Content-Style-Type" content="text/css"> |
| <style type="text/css"><!-- |
| pre.display { font-family:inherit } |
| pre.format { font-family:inherit } |
| pre.smalldisplay { font-family:inherit; font-size:smaller } |
| pre.smallformat { font-family:inherit; font-size:smaller } |
| pre.smallexample { font-size:smaller } |
| pre.smalllisp { font-size:smaller } |
| span.sc { font-variant:small-caps } |
| span.roman { font-family:serif; font-weight:normal; } |
| span.sansserif { font-family:sans-serif; font-weight:normal; } |
| --></style> |
| <link rel="stylesheet" type="text/css" href="../cs.css"> |
| </head> |
| <body> |
| <div class="node"> |
| <a name="Symbol-Value"></a> |
| <p> |
| Next: <a rel="next" accesskey="n" href="Symbol-Type.html#Symbol-Type">Symbol Type</a>, |
| Up: <a rel="up" accesskey="u" href="Symbol-Attributes.html#Symbol-Attributes">Symbol Attributes</a> |
| <hr> |
| </div> |
| |
| <h4 class="subsection">5.5.1 Value</h4> |
| |
| <p><a name="index-value-of-a-symbol-227"></a><a name="index-symbol-value-228"></a>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>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. |
| |
| </body></html> |
| |