1<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> 2<html> 3<!-- This file documents the gprof profiler of the GNU system. 4 5Copyright (C) 1988-2021 Free Software Foundation, Inc. 6 7Permission is granted to copy, distribute and/or modify this document 8under the terms of the GNU Free Documentation License, Version 1.3 9or any later version published by the Free Software Foundation; 10with no Invariant Sections, with no Front-Cover Texts, and with no 11Back-Cover Texts. A copy of the license is included in the 12section entitled "GNU Free Documentation License". 13 --> 14<!-- Created by GNU Texinfo 5.1, http://www.gnu.org/software/texinfo/ --> 15<head> 16<title>GNU gprof: Annotated Source</title> 17 18<meta name="description" content="GNU gprof: Annotated Source"> 19<meta name="keywords" content="GNU gprof: Annotated Source"> 20<meta name="resource-type" content="document"> 21<meta name="distribution" content="global"> 22<meta name="Generator" content="makeinfo"> 23<meta http-equiv="Content-Type" content="text/html; charset=utf-8"> 24<link href="index.html#Top" rel="start" title="Top"> 25<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents"> 26<link href="Output.html#Output" rel="up" title="Output"> 27<link href="Inaccuracy.html#Inaccuracy" rel="next" title="Inaccuracy"> 28<link href="Line_002dby_002dline.html#Line_002dby_002dline" rel="previous" title="Line-by-line"> 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="Annotated-Source"></a> 63<div class="header"> 64<p> 65Previous: <a href="Line_002dby_002dline.html#Line_002dby_002dline" accesskey="p" rel="previous">Line-by-line</a>, Up: <a href="Output.html#Output" accesskey="u" rel="up">Output</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>]</p> 66</div> 67<hr> 68<a name="The-Annotated-Source-Listing"></a> 69<h3 class="section">5.4 The Annotated Source Listing</h3> 70 71<p><code>gprof</code>’s ‘<samp>-A</samp>’ option triggers an annotated source listing, 72which lists the program’s source code, each function labeled with the 73number of times it was called. You may also need to specify the 74‘<samp>-I</samp>’ option, if <code>gprof</code> can’t find the source code files. 75</p> 76<p>With older versions of <code>gcc</code> compiling with ‘<samp>gcc … -g 77-pg -a</samp>’ augments your program with basic-block counting code, in 78addition to function counting code. This enables <code>gprof</code> to 79determine how many times each line of code was executed. With newer 80versions of <code>gcc</code> support for displaying basic-block counts is 81provided by the <code>gcov</code> program. 82</p> 83<p>For example, consider the following function, taken from gzip, 84with line numbers added: 85</p> 86<div class="smallexample"> 87<pre class="smallexample"> 1 ulg updcrc(s, n) 88 2 uch *s; 89 3 unsigned n; 90 4 { 91 5 register ulg c; 92 6 93 7 static ulg crc = (ulg)0xffffffffL; 94 8 95 9 if (s == NULL) { 9610 c = 0xffffffffL; 9711 } else { 9812 c = crc; 9913 if (n) do { 10014 c = crc_32_tab[...]; 10115 } while (--n); 10216 } 10317 crc = c; 10418 return c ^ 0xffffffffL; 10519 } 106 107</pre></div> 108 109<p><code>updcrc</code> has at least five basic-blocks. 110One is the function itself. The 111<code>if</code> statement on line 9 generates two more basic-blocks, one 112for each branch of the <code>if</code>. A fourth basic-block results from 113the <code>if</code> on line 13, and the contents of the <code>do</code> loop form 114the fifth basic-block. The compiler may also generate additional 115basic-blocks to handle various special cases. 116</p> 117<p>A program augmented for basic-block counting can be analyzed with 118‘<samp>gprof -l -A</samp>’. 119The ‘<samp>-x</samp>’ option is also helpful, 120to ensure that each line of code is labeled at least once. 121Here is <code>updcrc</code>’s 122annotated source listing for a sample <code>gzip</code> run: 123</p> 124<div class="smallexample"> 125<pre class="smallexample"> ulg updcrc(s, n) 126 uch *s; 127 unsigned n; 128 2 ->{ 129 register ulg c; 130 131 static ulg crc = (ulg)0xffffffffL; 132 133 2 -> if (s == NULL) { 134 1 -> c = 0xffffffffL; 135 1 -> } else { 136 1 -> c = crc; 137 1 -> if (n) do { 138 26312 -> c = crc_32_tab[...]; 13926312,1,26311 -> } while (--n); 140 } 141 2 -> crc = c; 142 2 -> return c ^ 0xffffffffL; 143 2 ->} 144</pre></div> 145 146<p>In this example, the function was called twice, passing once through 147each branch of the <code>if</code> statement. The body of the <code>do</code> 148loop was executed a total of 26312 times. Note how the <code>while</code> 149statement is annotated. It began execution 26312 times, once for 150each iteration through the loop. One of those times (the last time) 151it exited, while it branched back to the beginning of the loop 26311 times. 152</p> 153<hr> 154<div class="header"> 155<p> 156Previous: <a href="Line_002dby_002dline.html#Line_002dby_002dline" accesskey="p" rel="previous">Line-by-line</a>, Up: <a href="Output.html#Output" accesskey="u" rel="up">Output</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>]</p> 157</div> 158 159 160 161</body> 162</html> 163