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155 lines
9.2 KiB
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
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<html>
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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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<tr>
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<td colspan="2" height="64"> </td>
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</tr>
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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><br />
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<a href="#BOOST_VERIFY_MSG">BOOST_VERIFY_MSG</a><br />
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<a href="#BOOST_ASSERT_IS_VOID">BOOST_ASSERT_IS_VOID</a><br />
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</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 <code><boost/assert.hpp></code> defines the macro <code>BOOST_ASSERT</code>,
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which is similar to the standard <code>assert</code> macro defined in <code><cassert></code>.
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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, <code>BOOST_ASSERT(expr)</code> expands to <code>assert(expr)</code>.</p>
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<p>• If the macro <code>BOOST_DISABLE_ASSERTS</code> is defined when <code><boost/assert.hpp></code>
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is included, <code>BOOST_ASSERT(expr)</code> expands to <code>((void)0)</code>, regardless of whether
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the macro <code>NDEBUG</code> is defined. This allows users to selectively disable <code>BOOST_ASSERT</code> without
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affecting the definition of the standard <code>assert</code>.</p>
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<p>• If the macro <code>BOOST_ENABLE_ASSERT_HANDLER</code> is defined when <code><boost/assert.hpp></code>
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is included, <code>BOOST_ASSERT(expr)</code> expands to</p>
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<blockquote>
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<pre>(<a href="../config/doc/html/boost_config/boost_macro_reference.html#boost_config.boost_macro_reference.boost_helper_macros">BOOST_LIKELY</a>(!!(expr))? ((void)0): ::boost::assertion_failed(#expr, <a href="current_function.html">BOOST_CURRENT_FUNCTION</a>, __FILE__, __LINE__))</pre>
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</blockquote>
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<p>That is, it evaluates <code>expr</code> and if it's false, calls <code>::boost::assertion_failed(#expr, BOOST_CURRENT_FUNCTION, __FILE__, __LINE__)</code>.
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This is true regardless of whether <code>NDEBUG</code> is defined.</p>
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<p><code>boost::assertion_failed</code> is declared in <code><boost/assert.hpp></code> 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>• If the macro <code>BOOST_ENABLE_ASSERT_DEBUG_HANDLER</code> is defined when <code><boost/assert.hpp></code>
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is included, <code>BOOST_ASSERT(expr)</code> expands to <code>((void)0)</code> when <code>NDEBUG</code> is
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defined. Otherwise the behavior is as if <code>BOOST_ENABLE_ASSERT_HANDLER</code> has been defined.</p>
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<p>As is the case with <code><cassert></code>, <code><boost/assert.hpp></code>
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can be included multiple times in a single translation unit. <code>BOOST_ASSERT</code>
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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 macro <code>BOOST_ASSERT_MSG</code> is similar to <code>BOOST_ASSERT</code>, but it takes an additional argument,
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a character literal, supplying an error message.</p>
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<p>• By default, <code>BOOST_ASSERT_MSG(expr,msg)</code> expands to <code>assert((expr)&&(msg))</code>.</p>
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<p>• If the macro <code>BOOST_DISABLE_ASSERTS</code> is defined when <code><boost/assert.hpp></code>
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is included, <code>BOOST_ASSERT_MSG(expr,msg)</code> expands to <code>((void)0)</code>, regardless of whether
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the macro <code>NDEBUG</code> is defined.</p>
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<p>• If the macro <code>BOOST_ENABLE_ASSERT_HANDLER</code> is defined when <code><boost/assert.hpp></code>
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is included, <code>BOOST_ASSERT_MSG(expr,msg)</code> expands to</p>
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<blockquote>
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<pre>(<a href="../config/doc/html/boost_config/boost_macro_reference.html#boost_config.boost_macro_reference.boost_helper_macros">BOOST_LIKELY</a>(!!(expr))? ((void)0): ::boost::assertion_failed_msg(#expr, msg, <a href="current_function.html">BOOST_CURRENT_FUNCTION</a>, __FILE__, __LINE__))</pre>
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</blockquote>
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<p>This is true regardless of whether <code>NDEBUG</code> is defined.</p>
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<p><code>boost::assertion_failed_msg</code> is declared in <code><boost/assert.hpp></code> 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>• If the macro <code>BOOST_ENABLE_ASSERT_DEBUG_HANDLER</code> is defined when <code><boost/assert.hpp></code>
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is included, <code>BOOST_ASSERT_MSG(expr)</code> expands to <code>((void)0)</code> when <code>NDEBUG</code> is
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defined. Otherwise the behavior is as if <code>BOOST_ENABLE_ASSERT_HANDLER</code> has been defined.</p>
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<p>As is the case with <code><cassert></code>, <code><boost/assert.hpp></code>
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can be included multiple times in a single translation unit. <code>BOOST_ASSERT_MSG</code>
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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>The macro <code>BOOST_VERIFY</code> has the same behavior as <code>BOOST_ASSERT</code>, except that
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the expression that is passed to <code>BOOST_VERIFY</code> 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>• If the macro <code>BOOST_DISABLE_ASSERTS</code> is defined when <code><boost/assert.hpp></code>
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is included, <code>BOOST_VERIFY(expr)</code> expands to <code>((void)(expr))</code>.</p>
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<p>• If the macro <code>BOOST_ENABLE_ASSERT_HANDLER</code> is defined when <code><boost/assert.hpp></code>
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is included, <code>BOOST_VERIFY(expr)</code> expands to <code>BOOST_ASSERT(expr)</code>.</p>
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<p>• Otherwise, <code>BOOST_VERIFY(expr)</code> expands to <code>((void)(expr))</code> when <code>NDEBUG</code> is
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defined, to <code>BOOST_ASSERT(expr)</code> when it's not.</p>
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<h2><a name="BOOST_VERIFY_MSG">BOOST_VERIFY_MSG</a></h2>
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<p>The macro <code>BOOST_VERIFY_MSG</code> is similar to <code>BOOST_VERIFY</code>, with an additional parameter, an error message.</p>
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<p>• If the macro <code>BOOST_DISABLE_ASSERTS</code> is defined when <code><boost/assert.hpp></code>
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is included, <code>BOOST_VERIFY_MSG(expr,msg)</code> expands to <code>((void)(expr))</code>.</p>
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<p>• If the macro <code>BOOST_ENABLE_ASSERT_HANDLER</code> is defined when <code><boost/assert.hpp></code>
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is included, <code>BOOST_VERIFY_MSG(expr,msg)</code> expands to <code>BOOST_ASSERT_MSG(expr,msg)</code>.</p>
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<p>• Otherwise, <code>BOOST_VERIFY_MSG(expr,msg)</code> expands to <code>((void)(expr))</code> when <code>NDEBUG</code> is
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defined, to <code>BOOST_ASSERT_MSG(expr,msg)</code> when it's not.</p>
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<hr />
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<p>
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<h2><a name="BOOST_ASSERT_IS_VOID">BOOST_ASSERT_IS_VOID</a></h2>
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<p>The macro <code>BOOST_ASSERT_IS_VOID</code> is defined when <code>BOOST_ASSERT</code> and <code>BOOST_ASSERT_MSG</code>, are expanded to <code>((void)0)</code>.
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This macro is useful to avoid compiling and potentially running code that is only intended to prepare data to be used in the assertion.</p>
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<blockquote>
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<pre>
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void MyContainer::erase(iterator i)
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{
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//Some sanity checks, data must be ordered
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#ifndef BOOST_ASSERT_IS_VOID
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if(i != c.begin()){
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iterator prev = i;
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--prev;
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BOOST_ASSERT(*prev < *i);
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}
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else if(i != c.end()){
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iterator next = i;
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++next;
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BOOST_ASSERT(*i < *next);
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}
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#endif
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this->erase_impl(i);
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}
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</pre>
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</blockquote>
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<p>• By default, <code>BOOST_ASSERT_IS_VOID</code> is defined if <code>NDEBUG</code> is defined.</p>
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<p>• If the macro <code>BOOST_DISABLE_ASSERTS</code> is defined <code>BOOST_ASSERT_IS_VOID</code> is always defined.</p>
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<p>• If the macro <code>BOOST_ENABLE_ASSERT_HANDLER</code> is defined <code>BOOST_ASSERT_IS_VOID</code> is never defined.</p>
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<p>• If the macro <code>BOOST_ENABLE_ASSERT_DEBUG_HANDLER</code>, then <code>BOOST_ASSERT_IS_VOID</code> is defined when <code>NDEBUG</code> is defined.</p>
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<hr />
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<p>
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<small>Copyright <20> 2002, 2007, 2014 by Peter Dimov. Copyright <20> 2011
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by Beman Dawes. Copyright <20> 2015 by Ion Gaztanaga. 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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</body>
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</html>
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