1<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> 2<html> 3<!-- Copyright (C) 1992-2021 Free Software Foundation, Inc. 4Contributed by Cygnus Support. Written by Julia Menapace, Jim Kingdon, 5and David MacKenzie. 6 7Permission is granted to copy, distribute and/or modify this document 8under the terms of the GNU Free Documentation License, Version 1.3 or 9any later version published by the Free Software Foundation; with no 10Invariant Sections, with no Front-Cover Texts, and with no Back-Cover 11Texts. A copy of the license is included in the section entitled "GNU 12Free Documentation License". --> 13<!-- Created by GNU Texinfo 5.1, http://www.gnu.org/software/texinfo/ --> 14<head> 15<title>STABS: Global Variables</title> 16 17<meta name="description" content="STABS: Global Variables"> 18<meta name="keywords" content="STABS: Global Variables"> 19<meta name="resource-type" content="document"> 20<meta name="distribution" content="global"> 21<meta name="Generator" content="makeinfo"> 22<meta http-equiv="Content-Type" content="text/html; charset=utf-8"> 23<link href="index.html#Top" rel="start" title="Top"> 24<link href="Symbol-Types-Index.html#Symbol-Types-Index" rel="index" title="Symbol Types Index"> 25<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents"> 26<link href="Variables.html#Variables" rel="up" title="Variables"> 27<link href="Register-Variables.html#Register-Variables" rel="next" title="Register Variables"> 28<link href="Stack-Variables.html#Stack-Variables" rel="previous" title="Stack Variables"> 29<style type="text/css"> 30<!-- 31a.summary-letter {text-decoration: none} 32blockquote.smallquotation {font-size: smaller} 33div.display {margin-left: 3.2em} 34div.example {margin-left: 3.2em} 35div.indentedblock {margin-left: 3.2em} 36div.lisp {margin-left: 3.2em} 37div.smalldisplay {margin-left: 3.2em} 38div.smallexample {margin-left: 3.2em} 39div.smallindentedblock {margin-left: 3.2em; font-size: smaller} 40div.smalllisp {margin-left: 3.2em} 41kbd {font-style:oblique} 42pre.display {font-family: inherit} 43pre.format {font-family: inherit} 44pre.menu-comment {font-family: serif} 45pre.menu-preformatted {font-family: serif} 46pre.smalldisplay {font-family: inherit; font-size: smaller} 47pre.smallexample {font-size: smaller} 48pre.smallformat {font-family: inherit; font-size: smaller} 49pre.smalllisp {font-size: smaller} 50span.nocodebreak {white-space:nowrap} 51span.nolinebreak {white-space:nowrap} 52span.roman {font-family:serif; font-weight:normal} 53span.sansserif {font-family:sans-serif; font-weight:normal} 54ul.no-bullet {list-style: none} 55--> 56</style> 57 58 59</head> 60 61<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000"> 62<a name="Global-Variables"></a> 63<div class="header"> 64<p> 65Next: <a href="Register-Variables.html#Register-Variables" accesskey="n" rel="next">Register Variables</a>, Previous: <a href="Stack-Variables.html#Stack-Variables" accesskey="p" rel="previous">Stack Variables</a>, Up: <a href="Variables.html#Variables" accesskey="u" rel="up">Variables</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Symbol-Types-Index.html#Symbol-Types-Index" title="Index" rel="index">Index</a>]</p> 66</div> 67<hr> 68<a name="Global-Variables-1"></a> 69<h3 class="section">4.2 Global Variables</h3> 70 71<a name="index-N_005fGSYM"></a> 72<a name="index-C_005fGSYM"></a> 73<p>A variable whose scope is not specific to just one source file is 74represented by the ‘<samp>G</samp>’ symbol descriptor. These stabs use the 75<code>N_GSYM</code> stab type (C_GSYM for XCOFF). The type information for 76the stab (see <a href="String-Field.html#String-Field">String Field</a>) gives the type of the variable. 77</p> 78<p>For example, the following source code: 79</p> 80<div class="example"> 81<pre class="example">char g_foo = 'c'; 82</pre></div> 83 84<p>yields the following assembly code: 85</p> 86<div class="example"> 87<pre class="example">.stabs "g_foo:G2",32,0,0,0 # <span class="roman">32 is N_GSYM</span> 88 .global _g_foo 89 .data 90_g_foo: 91 .byte 99 92</pre></div> 93 94<p>The address of the variable represented by the <code>N_GSYM</code> is not 95contained in the <code>N_GSYM</code> stab. The debugger gets this information 96from the external symbol for the global variable. In the example above, 97the <code>.global _g_foo</code> and <code>_g_foo:</code> lines tell the assembler to 98produce an external symbol. 99</p> 100<p>Some compilers, like GCC, output <code>N_GSYM</code> stabs only once, where 101the variable is defined. Other compilers, like SunOS4 /bin/cc, output a 102<code>N_GSYM</code> stab for each compilation unit which references the 103variable. 104</p> 105 106 107 108</body> 109</html> 110