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<h3 class="section">10.4 Brief Description of <samp><span class="command">gcov</span></samp> Data Files</h3>
<p><samp><span class="command">gcov</span></samp> uses two files for profiling. The names of these files
are derived from the original <em>object</em> file by substituting the
file suffix with either <samp><span class="file">.gcno</span></samp>, or <samp><span class="file">.gcda</span></samp>. The files
contain coverage and profile data stored in a platform-independent format.
The <samp><span class="file">.gcno</span></samp> files are placed in the same directory as the object
file. By default, the <samp><span class="file">.gcda</span></samp> files are also stored in the same
directory as the object file, but the GCC <samp><span class="option">-fprofile-dir</span></samp> option
may be used to store the <samp><span class="file">.gcda</span></samp> files in a separate directory.
<p>The <samp><span class="file">.gcno</span></samp> notes file is generated when the source file is compiled
with the GCC <samp><span class="option">-ftest-coverage</span></samp> option. It contains information to
reconstruct the basic block graphs and assign source line numbers to
blocks.
<p>The <samp><span class="file">.gcda</span></samp> count data file is generated when a program containing
object files built with the GCC <samp><span class="option">-fprofile-arcs</span></samp> option is executed.
A separate <samp><span class="file">.gcda</span></samp> file is created for each object file compiled with
this option. It contains arc transition counts, value profile counts, and
some summary information.
<p>The full details of the file format is specified in <samp><span class="file">gcov-io.h</span></samp>,
and functions provided in that header file should be used to access the
coverage files.
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