1<html lang="en"> 2<head> 3<title>Cross-profiling - Using the GNU Compiler Collection (GCC)</title> 4<meta http-equiv="Content-Type" content="text/html"> 5<meta name="description" content="Using the GNU Compiler Collection (GCC)"> 6<meta name="generator" content="makeinfo 4.13"> 7<link title="Top" rel="start" href="index.html#Top"> 8<link rel="up" href="Gcov.html#Gcov" title="Gcov"> 9<link rel="prev" href="Gcov-Data-Files.html#Gcov-Data-Files" title="Gcov Data Files"> 10<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage"> 11<!-- 12Copyright (C) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 131998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 142010 Free Software Foundation, Inc. 15 16Permission is granted to copy, distribute and/or modify this document 17under the terms of the GNU Free Documentation License, Version 1.3 or 18any later version published by the Free Software Foundation; with the 19Invariant Sections being ``Funding Free Software'', the Front-Cover 20Texts being (a) (see below), and with the Back-Cover Texts being (b) 21(see below). A copy of the license is included in the section entitled 22``GNU Free Documentation License''. 23 24(a) The FSF's Front-Cover Text is: 25 26 A GNU Manual 27 28(b) The FSF's Back-Cover Text is: 29 30 You have freedom to copy and modify this GNU Manual, like GNU 31 software. Copies published by the Free Software Foundation raise 32 funds for GNU development.--> 33<meta http-equiv="Content-Style-Type" content="text/css"> 34<style type="text/css"><!-- 35 pre.display { font-family:inherit } 36 pre.format { font-family:inherit } 37 pre.smalldisplay { font-family:inherit; font-size:smaller } 38 pre.smallformat { font-family:inherit; font-size:smaller } 39 pre.smallexample { font-size:smaller } 40 pre.smalllisp { font-size:smaller } 41 span.sc { font-variant:small-caps } 42 span.roman { font-family:serif; font-weight:normal; } 43 span.sansserif { font-family:sans-serif; font-weight:normal; } 44--></style> 45<link rel="stylesheet" type="text/css" href="../cs.css"> 46</head> 47<body> 48<div class="node"> 49<a name="Cross-profiling"></a> 50<a name="Cross_002dprofiling"></a> 51<p> 52Previous: <a rel="previous" accesskey="p" href="Gcov-Data-Files.html#Gcov-Data-Files">Gcov Data Files</a>, 53Up: <a rel="up" accesskey="u" href="Gcov.html#Gcov">Gcov</a> 54<hr> 55</div> 56 57<h3 class="section">10.5 Data file relocation to support cross-profiling</h3> 58 59<p>Running the program will cause profile output to be generated. For each 60source file compiled with <samp><span class="option">-fprofile-arcs</span></samp>, an accompanying <samp><span class="file">.gcda</span></samp> 61file will be placed in the object file directory. That implicitly requires 62running the program on the same system as it was built or having the same 63absolute directory structure on the target system. The program will try 64to create the needed directory structure, if it is not already present. 65 66 <p>To support cross-profiling, a program compiled with <samp><span class="option">-fprofile-arcs</span></samp> 67can relocate the data files based on two environment variables: 68 69 <ul> 70<li>GCOV_PREFIX contains the prefix to add to the absolute paths 71in the object file. Prefix can be absolute, or relative. The 72default is no prefix. 73 74 <li>GCOV_PREFIX_STRIP indicates the how many initial directory names to strip off 75the hardwired absolute paths. Default value is 0. 76 77 <p><em>Note:</em> If GCOV_PREFIX_STRIP is set without GCOV_PREFIX is undefined, 78 then a relative path is made out of the hardwired absolute paths. 79</ul> 80 81 <p>For example, if the object file <samp><span class="file">/user/build/foo.o</span></samp> was built with 82<samp><span class="option">-fprofile-arcs</span></samp>, the final executable will try to create the data file 83<samp><span class="file">/user/build/foo.gcda</span></samp> when running on the target system. This will 84fail if the corresponding directory does not exist and it is unable to create 85it. This can be overcome by, for example, setting the environment as 86‘<samp><span class="samp">GCOV_PREFIX=/target/run</span></samp>’ and ‘<samp><span class="samp">GCOV_PREFIX_STRIP=1</span></samp>’. Such a 87setting will name the data file <samp><span class="file">/target/run/build/foo.gcda</span></samp>. 88 89 <p>You must move the data files to the expected directory tree in order to 90use them for profile directed optimizations (<samp><span class="option">--use-profile</span></samp>), or to 91use the <samp><span class="command">gcov</span></samp> tool. 92 93<!-- Copyright (C) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998, --> 94<!-- 1999, 2000, 2001, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010 --> 95<!-- Free Software Foundation, Inc. --> 96<!-- This is part of the GCC manual. --> 97<!-- For copying conditions, see the file gcc.texi. --> 98 </body></html> 99 100