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<h2>13.5 <code>gprof</code> doesn't produce output</h2>

<p><em><strong>Q</strong>: Every time I run the profiler it says "gmon.out: no such file or
directory" and no profile is produced.  What is this <code>gmon.out</code>
file, and why won't <code>gprof</code> compute the profile?</em>

<br><p>
<p><strong>A</strong>:  <code>gmon.out</code> is the file with raw execution counts and timing
info that <code>gprof</code> needs to produce the profile.  The file is
written by the profiled program when it exits.  If the file isn't
created, it might be because of one of the following reasons:

<ul>
<li>You didn't compile and/or link your program with the <code>-pg</code> switch. 
Note that <strong>both</strong> compilation and link need to be done with
<code>-pg</code>, because the functions that actually write the results to
<code>gmon.out</code> are only linked in when GCC sees <code>-pg</code> on the link
command line.

<li>You have called <code>ld.exe</code> directly to link your program and forgot
to mention the files and switches necessary for the profiled program
operation.  You should use <code>gcc</code> to link your program instead of
calling the linker directly; a <code>-pg</code> switch to <code>gcc</code> is all
that it takes to make sure that the linker will get all the necessary
arguments<a rel=footnote href="faq25.html"><sup>22</sup></a>.

<li>Your program exited abnormally.  The function which generates
<code>gmon.out</code> is registered with the <code>atexit</code> library function,
and won't be called if the program was terminated in an abnormal way. 
Make sure that your program exits with a call to <code>exit</code> library
function or with a <code>return</code> statement in your <code>main</code> function. 
For example, if your program dies with an exception or a signal, you
need to install a handler for that signal and make it call <code>exit</code>. 
</ul>

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