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115 lines
6.1 KiB
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<title>Boost: assert.hpp documentation</title>
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<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
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<body bgcolor="white" style="MARGIN-LEFT: 5%; MARGIN-RIGHT: 5%">
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<table border="0" width="100%">
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<tr>
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<td width="277"><A href="../../index.htm"> <img src="../../boost.png" alt="boost.png (6897 bytes)" width="277" height="86" border="0"></A>
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</td>
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<td align="center">
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<h1>assert.hpp</h1>
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</td>
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<tr>
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<td colspan="2" height="64"> </td>
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</table>
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<p>
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<a href="#BOOST_ASSERT">BOOST_ASSERT</a><br>
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<a href="#BOOST_ASSERT_MSG">BOOST_ASSERT_MSG</a><br>
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<a href="#BOOST_VERIFY">BOOST_VERIFY</a></p>
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<h2><a name="BOOST_ASSERT">BOOST_ASSERT</a></h2>
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<p>
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The header <STRONG><boost/assert.hpp></STRONG> defines the macro <b>BOOST_ASSERT</b>,
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which is similar to the standard <STRONG>assert</STRONG> macro defined in <STRONG><cassert></STRONG>.
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The macro is intended to be used in both Boost libraries and user
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code.
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</p>
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<P>By default, <tt>BOOST_ASSERT(expr)</tt> is equivalent to <tt>assert(expr)</tt>.</P>
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<P>If the macro <STRONG>BOOST_DISABLE_ASSERTS</STRONG> is defined when <STRONG><boost/assert.hpp></STRONG>
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is included, <tt>BOOST_ASSERT(expr)</tt> is defined as <tt>((void)0)</tt>. This
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allows users to selectively disable <STRONG>BOOST_ASSERT</STRONG> without
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affecting the definition of the standard <STRONG>assert</STRONG>.</P>
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<P>If the macro <STRONG>BOOST_ENABLE_ASSERT_HANDLER</STRONG> is defined when <STRONG><boost/assert.hpp></STRONG>
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is included, <tt>BOOST_ASSERT(expr)</tt> evaluates <b>expr</b> and, if the
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result is false, evaluates the expression</P>
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<blockquote>
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<P><tt>::boost::assertion_failed(#expr, <a href="current_function.html">BOOST_CURRENT_FUNCTION</a>,
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__FILE__, __LINE__)</tt></P>
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</blockquote>
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<P><STRONG>assertion_failed</STRONG> is declared in <STRONG><boost/assert.hpp></STRONG>
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as</P>
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<blockquote>
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<pre>namespace boost
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{
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void assertion_failed(char const * expr, char const * function, char const * file, long line);
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}
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</pre>
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</blockquote>
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<p>but it is never defined. The user is expected to supply an appropriate
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definition.</p>
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<P>As is the case with <STRONG><cassert></STRONG>, <STRONG><boost/assert.hpp></STRONG>
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can be included multiple times in a single translation unit. <STRONG>BOOST_ASSERT</STRONG>
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will be redefined each time as specified above.</P>
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<h2><a name="BOOST_ASSERT_MSG">BOOST_ASSERT_MSG</a></h2>
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<p>
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The header <STRONG><boost/assert.hpp></STRONG> defines the macro <b>BOOST_ASSERT_MSG</b>,
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which is similar to the standard <STRONG>assert</STRONG> macro defined in <STRONG><cassert></STRONG>,
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but with an additional macro parameter supplying an error message. The macro is intended to be used in both Boost libraries
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and user code.
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</p>
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<P> <tt>BOOST_ASSERT_MSG(expr, msg)</tt> is equivalent to <code>
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((void)0)</code> if <b>BOOST_DISABLE_ASSERTS</b> or <b>NDEBUG</b> are
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defined or <code>expr</code> evaluates to <code>true</code>. If those
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macros and <STRONG>BOOST_ENABLE_ASSERT_HANDLER</STRONG> are not
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defined, and <code>expr</code> evaluates to <code>false</code>, an error
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message that includes <tt>#expr</tt>, <tt>msg</tt>, <tt> <a href="current_function.html">BOOST_CURRENT_FUNCTION</a></tt>, <tt>
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__FILE__</tt>, and <tt>__LINE__</tt> is sent to output stream <b>
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BOOST_ASSERT_MSG_OSTREAM</b>
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and <code>std::abort()</code> is called.</P>
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<P> <b>BOOST_ASSERT_MSG_OSTREAM</b> defines the output stream. It defaults to <code>std::cerr</code>.
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Integrated development environments (IDE's) like Microsoft Visual Studio
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may produce easier to understand output if messages go to a different
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stream, such as <code>std::cout</code>. Users may define <b>BOOST_ASSERT_MSG_OSTREAM</b> before including <STRONG><boost/assert.hpp></STRONG>
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to specify a different output stream. </P>
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<P>If the macro <STRONG>BOOST_ENABLE_ASSERT_HANDLER</STRONG> is defined when <STRONG><boost/assert.hpp></STRONG>
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is included, instead of sending a error message to an output
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stream, this expression is evaluated</P>
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<blockquote>
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<P><tt>::boost::assertion_failed_msg(#expr, msg, <a href="current_function.html">BOOST_CURRENT_FUNCTION</a>,
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__FILE__, __LINE__)</tt></P>
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</blockquote>
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<P><STRONG>assertion_failed_msg</STRONG> is declared in <STRONG><boost/assert.hpp></STRONG>
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as</P>
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<blockquote>
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<pre>namespace boost
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{
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void assertion_failed_msg(char const * expr, char const * msg, char const * function, char const * file, long line);
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}
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</pre>
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</blockquote>
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<p>but it is never defined. The user is expected to supply an appropriate
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definition.</p>
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<P>As is the case with <STRONG><cassert></STRONG>, <STRONG><boost/assert.hpp></STRONG>
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can be included multiple times in a single translation unit. <STRONG>BOOST_ASSERT_MSG</STRONG>
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will be redefined each time as specified above.</P>
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<h2><a name="BOOST_VERIFY">BOOST_VERIFY</a></h2>
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<p><STRONG><boost/assert.hpp></STRONG> also defines the macro <STRONG>BOOST_VERIFY</STRONG>.
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It has exactly the same behavior as <STRONG>BOOST_ASSERT</STRONG>, except that
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the expression that is passed to <STRONG>BOOST_VERIFY</STRONG> is always
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evaluated. This is useful when the asserted expression has desirable side
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effects; it can also help suppress warnings about unused variables when the
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only use of the variable is inside an assertion.</p>
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<p><br>
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<small>Copyright <20> 2002, 2007 by Peter Dimov. Copyright <20> 2011
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by Beman Dawes. Distributed under the Boost Software
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License, Version 1.0. See accompanying file <A href="../../LICENSE_1_0.txt">LICENSE_1_0.txt</A>
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or copy at <A href="http://www.boost.org/LICENSE_1_0.txt">http://www.boost.org/LICENSE_1_0.txt</A>.</small></p>
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