1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>Macro BOOST_VMD_ASSERT_IS_EMPTY</title> 5<link rel="stylesheet" href="../../../../doc/src/boostbook.css" type="text/css"> 6<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 7<link rel="home" href="index.html" title="Chapter 1. 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If it is not empty, it forces a compiler error.</p> 38<p>The macro is a variadic macro taking any input. For the VC++8 compiler (VS2005) the macro takes a single parameter of input to check and not variadic data.</p> 39<p>The macro normally checks for emptiness only in debug mode. However an end-user can force the macro to check or not check by defining the macro BOOST_VMD_ASSERT_DATA to 1 or 0 respectively.</p> 40<p>.... = variadic input, for VC++8 this must be a single parameter.</p> 41<pre class="programlisting"><span class="identifier">returns</span> <span class="special">=</span> <span class="identifier">Normally</span> <span class="identifier">the</span> <span class="identifier">macro</span> <span class="identifier">returns</span> <span class="identifier">nothing</span><span class="special">.</span> 42 43 <span class="identifier">If</span> <span class="identifier">the</span> <span class="identifier">input</span> <span class="identifier">is</span> <span class="identifier">empty</span><span class="special">,</span> <span class="identifier">nothing</span> <span class="identifier">is</span> <span class="identifier">output</span><span class="special">.</span> 44 45 <span class="identifier">For</span> <span class="identifier">VC</span><span class="special">++</span><span class="special">,</span> <span class="identifier">because</span> <span class="identifier">there</span> <span class="identifier">is</span> <span class="identifier">no</span> <span class="identifier">sure</span> <span class="identifier">way</span> <span class="identifier">of</span> <span class="identifier">forcing</span> 46 <span class="identifier">a</span> <span class="identifier">compiler</span> <span class="identifier">error</span> <span class="identifier">from</span> <span class="identifier">within</span> <span class="identifier">a</span> <span class="identifier">macro</span> <span class="identifier">without</span> <span class="identifier">producing</span> 47 <span class="identifier">output</span><span class="special">,</span> <span class="keyword">if</span> <span class="identifier">the</span> <span class="identifier">input</span> <span class="identifier">is</span> <span class="identifier">not</span> <span class="identifier">empty</span> <span class="identifier">the</span> 48 <span class="identifier">macro</span> <span class="identifier">forces</span> <span class="identifier">a</span> <span class="identifier">compiler</span> <span class="identifier">error</span> <span class="identifier">by</span> <span class="identifier">outputting</span> <span class="identifier">invalid</span> <span class="identifier">C</span><span class="special">++</span><span class="special">.</span> 49 50 <span class="identifier">For</span> <span class="identifier">all</span> <span class="identifier">other</span> <span class="identifier">compilers</span> <span class="identifier">a</span> <span class="identifier">compiler</span> <span class="identifier">error</span> <span class="identifier">is</span> <span class="identifier">forced</span> 51 <span class="identifier">without</span> <span class="identifier">producing</span> <span class="identifier">output</span> <span class="keyword">if</span> <span class="identifier">the</span> <span class="identifier">input</span> <span class="identifier">is</span> <span class="identifier">not</span> <span class="identifier">empty</span><span class="special">.</span> 52</pre> 53<p>It is recommended to append BOOST_PP_EMPTY() to whatever input is being tested in order to avoid possible warning messages from some compilers about no parameters being passed to the macro when the input is truly empty. </p> 54</div> 55</div> 56<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 57<td align="left"></td> 58<td align="right"><div class="copyright-footer">Copyright © 2010-2017 Tropic Software 59 East Inc</div></td> 60</tr></table> 61<hr> 62<div class="spirit-nav"> 63<a accesskey="p" href="header/boost/vmd/assert_is_empty_hpp.html"><img src="../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="header/boost/vmd/assert_is_empty_hpp.html"><img src="../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="index.html"><img src="../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="header/boost/vmd/assert_is_identifier_hpp.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a> 64</div> 65</body> 66</html> 67
