120 lines
5.3 KiB
HTML
120 lines
5.3 KiB
HTML
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3 or
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any later version published by the Free Software Foundation; with the
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Invariant Sections being "Funding Free Software", the Front-Cover
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Texts being (a) (see below), and with the Back-Cover Texts being (b)
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(see below). A copy of the license is included in the section entitled
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"GNU Free Documentation License".
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(a) The FSF's Front-Cover Text is:
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A GNU Manual
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(b) The FSF's Back-Cover Text is:
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<!-- Created by GNU Texinfo 5.2, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>Using the GNU Compiler Collection (GCC): Cross-profiling</title>
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<meta name="description" content="Using the GNU Compiler Collection (GCC): Cross-profiling">
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<meta name="keywords" content="Using the GNU Compiler Collection (GCC): Cross-profiling">
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<meta name="resource-type" content="document">
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<meta name="distribution" content="global">
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<meta name="Generator" content="makeinfo">
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<link href="index.html#Top" rel="start" title="Top">
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<link href="Option-Index.html#Option-Index" rel="index" title="Option Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Gcov.html#Gcov" rel="up" title="Gcov">
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<link href="Gcov_002dtool.html#Gcov_002dtool" rel="next" title="Gcov-tool">
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<link href="Gcov-Data-Files.html#Gcov-Data-Files" rel="prev" title="Gcov Data Files">
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<style type="text/css">
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</head>
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<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
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<a name="Cross_002dprofiling"></a>
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<div class="header">
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<p>
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Previous: <a href="Gcov-Data-Files.html#Gcov-Data-Files" accesskey="p" rel="prev">Gcov Data Files</a>, Up: <a href="Gcov.html#Gcov" accesskey="u" rel="up">Gcov</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="Data-File-Relocation-to-Support-Cross_002dProfiling"></a>
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<h3 class="section">10.5 Data File Relocation to Support Cross-Profiling</h3>
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<p>Running the program will cause profile output to be generated. For each
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source file compiled with <samp>-fprofile-arcs</samp>, an accompanying <samp>.gcda</samp>
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file will be placed in the object file directory. That implicitly requires
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running the program on the same system as it was built or having the same
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absolute directory structure on the target system. The program will try
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to create the needed directory structure, if it is not already present.
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</p>
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<p>To support cross-profiling, a program compiled with <samp>-fprofile-arcs</samp>
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can relocate the data files based on two environment variables:
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</p>
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<ul>
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<li> GCOV_PREFIX contains the prefix to add to the absolute paths
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in the object file. Prefix can be absolute, or relative. The
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default is no prefix.
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</li><li> GCOV_PREFIX_STRIP indicates the how many initial directory names to strip off
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the hardwired absolute paths. Default value is 0.
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<p><em>Note:</em> If GCOV_PREFIX_STRIP is set without GCOV_PREFIX is undefined,
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then a relative path is made out of the hardwired absolute paths.
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</p></li></ul>
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<p>For example, if the object file <samp>/user/build/foo.o</samp> was built with
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<samp>-fprofile-arcs</samp>, the final executable will try to create the data file
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<samp>/user/build/foo.gcda</samp> when running on the target system. This will
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fail if the corresponding directory does not exist and it is unable to create
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it. This can be overcome by, for example, setting the environment as
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‘<samp>GCOV_PREFIX=/target/run</samp>’ and ‘<samp>GCOV_PREFIX_STRIP=1</samp>’. Such a
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setting will name the data file <samp>/target/run/build/foo.gcda</samp>.
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</p>
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<p>You must move the data files to the expected directory tree in order to
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use them for profile directed optimizations (<samp>--use-profile</samp>), or to
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use the <code>gcov</code> tool.
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</p>
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</body>
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</html>
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