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Predefined preprocessor variables [C++ Reference]
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<h2><a name="predefined_preprocessor_variables" id="predefined_preprocessor_variables">Predefined preprocessor variables</a></h2>
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<p>
Syntax:
</p>
<pre class="c code c++" style="font-family:monospace;"> __LINE__
__FILE__
__DATE__
__TIME__
__cplusplus
__STDC__</pre>
<p>
The following variables can vary by compiler, but generally work:
</p>
<ul>
<li class="level1"><div class="li"> The <code>__LINE__</code> and <code>__FILE__</code> variables represent the current line and current file being processed.</div>
</li>
<li class="level1"><div class="li"> The <code>__DATE__</code> variable contains the current date, in the form month/day/year. This is the date that the file was compiled, not necessarily the current date.</div>
</li>
<li class="level1"><div class="li"> The <code>__TIME__</code> variable represents the current time, in the form hour:minute:second. This is the time that the file was compiled, not necessarily the current time.</div>
</li>
<li class="level1"><div class="li"> The <code>__cplusplus</code> variable is only defined when compiling a C++ program. In some older compilers, this is also called <code>c_plusplus</code>.</div>
</li>
<li class="level1"><div class="li"> The <code>__STDC__</code> variable is defined when compiling a C program, and may also be defined when compiling C++.</div>
</li>
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<h3><a name="gcc-specific_variables" id="gcc-specific_variables">GCC-specific variables</a></h3>
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The following are GCC-specific variables. While they are not specifically preprocessor macros they are <a href="http://gcc.gnu.org/onlinedocs/gcc/Function-Names.html" class="urlextern" title="http://gcc.gnu.org/onlinedocs/gcc/Function-Names.html" rel="nofollow">magic</a> and can be used the same way:
</p>
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<li class="level1"><div class="li"> <code>__func__</code> contains the bare name of the function</div>
</li>
<li class="level1"><div class="li"> <code>__FUNCTION__</code> is another name for <code>__func__</code></div>
</li>
<li class="level1"><div class="li"> The <code>__PRETTY_FUNCTION__</code> contains the type signature of the function as well as its bare name. </div>
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