1<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> 2<html> 3<!-- Copyright (C) 1988-2021 Free Software Foundation, Inc. 4 5Permission is granted to copy, distribute and/or modify this document 6under the terms of the GNU Free Documentation License, Version 1.3 or 7any later version published by the Free Software Foundation; with the 8Invariant Sections being "Free Software" and "Free Software Needs 9Free Documentation", with the Front-Cover Texts being "A GNU Manual," 10and with the Back-Cover Texts as in (a) below. 11 12(a) The FSF's Back-Cover Text is: "You are free to copy and modify 13this GNU Manual. Buying copies from GNU Press supports the FSF in 14developing GNU and promoting software freedom." --> 15<!-- Created by GNU Texinfo 5.1, http://www.gnu.org/software/texinfo/ --> 16<head> 17<title>Debugging with GDB: Line Tables In Python</title> 18 19<meta name="description" content="Debugging with GDB: Line Tables In Python"> 20<meta name="keywords" content="Debugging with GDB: Line Tables In Python"> 21<meta name="resource-type" content="document"> 22<meta name="distribution" content="global"> 23<meta name="Generator" content="makeinfo"> 24<meta http-equiv="Content-Type" content="text/html; charset=utf-8"> 25<link href="index.html#Top" rel="start" title="Top"> 26<link href="Concept-Index.html#Concept-Index" rel="index" title="Concept Index"> 27<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents"> 28<link href="Python-API.html#Python-API" rel="up" title="Python API"> 29<link href="Breakpoints-In-Python.html#Breakpoints-In-Python" rel="next" title="Breakpoints In Python"> 30<link href="Symbol-Tables-In-Python.html#Symbol-Tables-In-Python" rel="previous" title="Symbol Tables In Python"> 31<style type="text/css"> 32<!-- 33a.summary-letter {text-decoration: none} 34blockquote.smallquotation {font-size: smaller} 35div.display {margin-left: 3.2em} 36div.example {margin-left: 3.2em} 37div.indentedblock {margin-left: 3.2em} 38div.lisp {margin-left: 3.2em} 39div.smalldisplay {margin-left: 3.2em} 40div.smallexample {margin-left: 3.2em} 41div.smallindentedblock {margin-left: 3.2em; font-size: smaller} 42div.smalllisp {margin-left: 3.2em} 43kbd {font-style:oblique} 44pre.display {font-family: inherit} 45pre.format {font-family: inherit} 46pre.menu-comment {font-family: serif} 47pre.menu-preformatted {font-family: serif} 48pre.smalldisplay {font-family: inherit; font-size: smaller} 49pre.smallexample {font-size: smaller} 50pre.smallformat {font-family: inherit; font-size: smaller} 51pre.smalllisp {font-size: smaller} 52span.nocodebreak {white-space:nowrap} 53span.nolinebreak {white-space:nowrap} 54span.roman {font-family:serif; font-weight:normal} 55span.sansserif {font-family:sans-serif; font-weight:normal} 56ul.no-bullet {list-style: none} 57--> 58</style> 59 60 61</head> 62 63<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000"> 64<a name="Line-Tables-In-Python"></a> 65<div class="header"> 66<p> 67Next: <a href="Breakpoints-In-Python.html#Breakpoints-In-Python" accesskey="n" rel="next">Breakpoints In Python</a>, Previous: <a href="Symbol-Tables-In-Python.html#Symbol-Tables-In-Python" accesskey="p" rel="previous">Symbol Tables In Python</a>, Up: <a href="Python-API.html#Python-API" accesskey="u" rel="up">Python API</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p> 68</div> 69<hr> 70<a name="Manipulating-line-tables-using-Python"></a> 71<h4 class="subsubsection">23.2.2.29 Manipulating line tables using Python</h4> 72 73<a name="index-line-tables-in-python"></a> 74<a name="index-gdb_002eLineTable"></a> 75 76<p>Python code can request and inspect line table information from a 77symbol table that is loaded in <small>GDB</small>. A line table is a 78mapping of source lines to their executable locations in memory. To 79acquire the line table information for a particular symbol table, use 80the <code>linetable</code> function (see <a href="Symbol-Tables-In-Python.html#Symbol-Tables-In-Python">Symbol Tables In Python</a>). 81</p> 82<p>A <code>gdb.LineTable</code> is iterable. The iterator returns 83<code>LineTableEntry</code> objects that correspond to the source line and 84address for each line table entry. <code>LineTableEntry</code> objects have 85the following attributes: 86</p> 87<dl> 88<dt><a name="index-LineTableEntry_002eline"></a>Variable: <strong>LineTableEntry.line</strong></dt> 89<dd><p>The source line number for this line table entry. This number 90corresponds to the actual line of source. This attribute is not 91writable. 92</p></dd></dl> 93 94<dl> 95<dt><a name="index-LineTableEntry_002epc"></a>Variable: <strong>LineTableEntry.pc</strong></dt> 96<dd><p>The address that is associated with the line table entry where the 97executable code for that source line resides in memory. This 98attribute is not writable. 99</p></dd></dl> 100 101<p>As there can be multiple addresses for a single source line, you may 102receive multiple <code>LineTableEntry</code> objects with matching 103<code>line</code> attributes, but with different <code>pc</code> attributes. The 104iterator is sorted in ascending <code>pc</code> order. Here is a small 105example illustrating iterating over a line table. 106</p> 107<div class="smallexample"> 108<pre class="smallexample">symtab = gdb.selected_frame().find_sal().symtab 109linetable = symtab.linetable() 110for line in linetable: 111 print "Line: "+str(line.line)+" Address: "+hex(line.pc) 112</pre></div> 113 114<p>This will have the following output: 115</p> 116<div class="smallexample"> 117<pre class="smallexample">Line: 33 Address: 0x4005c8L 118Line: 37 Address: 0x4005caL 119Line: 39 Address: 0x4005d2L 120Line: 40 Address: 0x4005f8L 121Line: 42 Address: 0x4005ffL 122Line: 44 Address: 0x400608L 123Line: 42 Address: 0x40060cL 124Line: 45 Address: 0x400615L 125</pre></div> 126 127<p>In addition to being able to iterate over a <code>LineTable</code>, it also 128has the following direct access methods: 129</p> 130<dl> 131<dt><a name="index-LineTable_002eline"></a>Function: <strong>LineTable.line</strong> <em>(line)</em></dt> 132<dd><p>Return a Python <code>Tuple</code> of <code>LineTableEntry</code> objects for any 133entries in the line table for the given <var>line</var>, which specifies 134the source code line. If there are no entries for that source code 135<var>line</var>, the Python <code>None</code> is returned. 136</p></dd></dl> 137 138<dl> 139<dt><a name="index-LineTable_002ehas_005fline"></a>Function: <strong>LineTable.has_line</strong> <em>(line)</em></dt> 140<dd><p>Return a Python <code>Boolean</code> indicating whether there is an entry in 141the line table for this source line. Return <code>True</code> if an entry 142is found, or <code>False</code> if not. 143</p></dd></dl> 144 145<dl> 146<dt><a name="index-LineTable_002esource_005flines"></a>Function: <strong>LineTable.source_lines</strong> <em>()</em></dt> 147<dd><p>Return a Python <code>List</code> of the source line numbers in the symbol 148table. Only lines with executable code locations are returned. The 149contents of the <code>List</code> will just be the source line entries 150represented as Python <code>Long</code> values. 151</p></dd></dl> 152 153<hr> 154<div class="header"> 155<p> 156Next: <a href="Breakpoints-In-Python.html#Breakpoints-In-Python" accesskey="n" rel="next">Breakpoints In Python</a>, Previous: <a href="Symbol-Tables-In-Python.html#Symbol-Tables-In-Python" accesskey="p" rel="previous">Symbol Tables In Python</a>, Up: <a href="Python-API.html#Python-API" accesskey="u" rel="up">Python API</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p> 157</div> 158 159 160 161</body> 162</html> 163