<html lang="en"> <head> <title>Word - Using as</title> <meta http-equiv="Content-Type" content="text/html"> <meta name="description" content="Using as"> <meta name="generator" content="makeinfo 4.7"> <link title="Top" rel="start" href="index.html#Top"> <link rel="up" href="Pseudo-Ops.html#Pseudo-Ops" title="Pseudo Ops"> <link rel="prev" href="Weakref.html#Weakref" title="Weakref"> <link rel="next" href="Deprecated.html#Deprecated" title="Deprecated"> <link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage"> <!-- This file documents the GNU Assembler "as". Copyright (C) 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000, 2001, 2002, 2006, 2007 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 1.1 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''. man end--> <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; } --></style> </head> <body> <div class="node"> <p> <a name="Word"></a>Next: <a rel="next" accesskey="n" href="Deprecated.html#Deprecated">Deprecated</a>, Previous: <a rel="previous" accesskey="p" href="Weakref.html#Weakref">Weakref</a>, Up: <a rel="up" accesskey="u" href="Pseudo-Ops.html#Pseudo-Ops">Pseudo Ops</a> <hr><br> </div> <h3 class="section">7.120 <code>.word </code><var>expressions</var></h3> <p><a name="index-_0040code_007bword_007d-directive-499"></a>This directive expects zero or more <var>expressions</var>, of any section, separated by commas. <p>The size of the number emitted, and its byte order, depend on what target computer the assembly is for. <!-- on amd29k, i960, sparc the "special treatment to support compilers" doesn't --> <!-- happen-32-bit addressability, period; no long/short jumps. --> <p><a name="index-difference-tables-altered-500"></a><a name="index-altered-difference-tables-501"></a><blockquote> <em>Warning: Special Treatment to support Compilers</em> </blockquote> <p>Machines with a 32-bit address space, but that do less than 32-bit addressing, require the following special treatment. If the machine of interest to you does 32-bit addressing (or doesn't require it; see <a href="Machine-Dependencies.html#Machine-Dependencies">Machine Dependencies</a>), you can ignore this issue. <p>In order to assemble compiler output into something that works, <span class="command">as</span> occasionally does strange things to <span class="samp">.word</span> directives. Directives of the form <span class="samp">.word sym1-sym2</span> are often emitted by compilers as part of jump tables. Therefore, when <span class="command">as</span> assembles a directive of the form <span class="samp">.word sym1-sym2</span>, and the difference between <code>sym1</code> and <code>sym2</code> does not fit in 16 bits, <span class="command">as</span> creates a <dfn>secondary jump table</dfn>, immediately before the next label. This secondary jump table is preceded by a short-jump to the first byte after the secondary table. This short-jump prevents the flow of control from accidentally falling into the new table. Inside the table is a long-jump to <code>sym2</code>. The original <span class="samp">.word</span> contains <code>sym1</code> minus the address of the long-jump to <code>sym2</code>. <p>If there were several occurrences of <span class="samp">.word sym1-sym2</span> before the secondary jump table, all of them are adjusted. If there was a <span class="samp">.word sym3-sym4</span>, that also did not fit in sixteen bits, a long-jump to <code>sym4</code> is included in the secondary jump table, and the <code>.word</code> directives are adjusted to contain <code>sym3</code> minus the address of the long-jump to <code>sym4</code>; and so on, for as many entries in the original jump table as necessary. <!-- end DIFF-TBL-KLUGE --> </body></html>