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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <html> <head> <title>Boost: assert.hpp documentation</title> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" /> </head> <body bgcolor="white" style="MARGIN-LEFT: 5%; MARGIN-RIGHT: 5%"> <table border="0" width="100%"> <tr> <td width="277"><a href="../../index.htm"> <img src="../../boost.png" alt="boost.png (6897 bytes)" width="277" height="86" border="0" /></a> </td> <td align="center"> <h1>assert.hpp</h1> </td> </tr> <tr> <td colspan="2" height="64"> </td> </tr> </table> <a href="#BOOST_ASSERT">BOOST_ASSERT</a> <a href="#BOOST_ASSERT_MSG">BOOST_ASSERT_MSG</a> <a href="#BOOST_VERIFY">BOOST_VERIFY</a> <a href="#BOOST_VERIFY_MSG">BOOST_VERIFY_MSG</a> <h2><a name="BOOST_ASSERT">BOOST_ASSERT</a></h2> The header <code><boost/assert.hpp></code> defines the macro <code>BOOST_ASSERT</code>, which is similar to the standard <code>assert</code> macro defined in <code><cassert></code>. The macro is intended to be used in both Boost libraries and user code. • By default, <code>BOOST_ASSERT(expr)</code> expands to <code>assert(expr)</code>. • If the macro <code>BOOST_DISABLE_ASSERTS</code> is defined when <code><boost/assert.hpp></code> is included, <code>BOOST_ASSERT(expr)</code> expands to <code>((void)0)</code>, regardless of whether the macro <code>NDEBUG</code> is defined. This allows users to selectively disable <code>BOOST_ASSERT</code> without affecting the definition of the standard <code>assert</code>. • If the macro <code>BOOST_ENABLE_ASSERT_HANDLER</code> is defined when <code><boost/assert.hpp></code> is included, <code>BOOST_ASSERT(expr)</code> expands to <blockquote> <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> </blockquote> That is, it evaluates <code>expr</code> and if it's false, calls <code>::boost::assertion_failed(#expr, BOOST_CURRENT_FUNCTION, __FILE__, __LINE__)</code>. This is true regardless of whether <code>NDEBUG</code> is defined. <code>boost::assertion_failed</code> is declared in <code><boost/assert.hpp></code> as <blockquote> <pre>namespace boost { void assertion_failed(char const * expr, char const * function, char const * file, long line); } </pre> </blockquote> but it is never defined. The user is expected to supply an appropriate definition. • If the macro <code>BOOST_ENABLE_ASSERT_DEBUG_HANDLER</code> is defined when <code><boost/assert.hpp></code> is included, <code>BOOST_ASSERT(expr)</code> expands to <code>((void)0)</code> when <code>NDEBUG</code> is defined. Otherwise the behavior is as if <code>BOOST_ENABLE_ASSERT_HANDLER</code> has been defined. As is the case with <code><cassert></code>, <code><boost/assert.hpp></code> can be included multiple times in a single translation unit. <code>BOOST_ASSERT</code> will be redefined each time as specified above. <h2><a name="BOOST_ASSERT_MSG">BOOST_ASSERT_MSG</a></h2> The macro <code>BOOST_ASSERT_MSG</code> is similar to <code>BOOST_ASSERT</code>, but it takes an additional argument, a character literal, supplying an error message. • By default, <code>BOOST_ASSERT_MSG(expr,msg)</code> expands to <code>assert((expr)&&(msg))</code>. • If the macro <code>BOOST_DISABLE_ASSERTS</code> is defined when <code><boost/assert.hpp></code> is included, <code>BOOST_ASSERT_MSG(expr,msg)</code> expands to <code>((void)0)</code>, regardless of whether the macro <code>NDEBUG</code> is defined. • If the macro <code>BOOST_ENABLE_ASSERT_HANDLER</code> is defined when <code><boost/assert.hpp></code> is included, <code>BOOST_ASSERT_MSG(expr,msg)</code> expands to <blockquote> <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> </blockquote> This is true regardless of whether <code>NDEBUG</code> is defined. <code>boost::assertion_failed_msg</code> is declared in <code><boost/assert.hpp></code> as <blockquote> <pre>namespace boost { void assertion_failed_msg(char const * expr, char const * msg, char const * function, char const * file, long line); } </pre> </blockquote> but it is never defined. The user is expected to supply an appropriate definition. • If the macro <code>BOOST_ENABLE_ASSERT_DEBUG_HANDLER</code> is defined when <code><boost/assert.hpp></code> is included, <code>BOOST_ASSERT_MSG(expr)</code> expands to <code>((void)0)</code> when <code>NDEBUG</code> is defined. Otherwise the behavior is as if <code>BOOST_ENABLE_ASSERT_HANDLER</code> has been defined. As is the case with <code><cassert></code>, <code><boost/assert.hpp></code> can be included multiple times in a single translation unit. <code>BOOST_ASSERT_MSG</code> will be redefined each time as specified above. <h2><a name="BOOST_VERIFY">BOOST_VERIFY</a></h2> The macro <code>BOOST_VERIFY</code> has the same behavior as <code>BOOST_ASSERT</code>, except that the expression that is passed to <code>BOOST_VERIFY</code> is always evaluated. This is useful when the asserted expression has desirable side effects; it can also help suppress warnings about unused variables when the only use of the variable is inside an assertion. • If the macro <code>BOOST_DISABLE_ASSERTS</code> is defined when <code><boost/assert.hpp></code> is included, <code>BOOST_VERIFY(expr)</code> expands to <code>((void)(expr))</code>. • If the macro <code>BOOST_ENABLE_ASSERT_HANDLER</code> is defined when <code><boost/assert.hpp></code> is included, <code>BOOST_VERIFY(expr)</code> expands to <code>BOOST_ASSERT(expr)</code>. • Otherwise, <code>BOOST_VERIFY(expr)</code> expands to <code>((void)(expr))</code> when <code>NDEBUG</code> is defined, to <code>BOOST_ASSERT(expr)</code> when it's not. <h2><a name="BOOST_VERIFY_MSG">BOOST_VERIFY_MSG</a></h2> The macro <code>BOOST_VERIFY_MSG</code> is similar to <code>BOOST_VERIFY</code>, with an additional parameter, an error message. • If the macro <code>BOOST_DISABLE_ASSERTS</code> is defined when <code><boost/assert.hpp></code> is included, <code>BOOST_VERIFY_MSG(expr,msg)</code> expands to <code>((void)(expr))</code>. • If the macro <code>BOOST_ENABLE_ASSERT_HANDLER</code> is defined when <code><boost/assert.hpp></code> is included, <code>BOOST_VERIFY_MSG(expr,msg)</code> expands to <code>BOOST_ASSERT_MSG(expr,msg)</code>. • Otherwise, <code>BOOST_VERIFY_MSG(expr,msg)</code> expands to <code>((void)(expr))</code> when <code>NDEBUG</code> is defined, to <code>BOOST_ASSERT_MSG(expr,msg)</code> when it's not. <hr /> Copyright � 2002, 2007, 2014 by Peter Dimov.  Copyright � 2011 by Beman Dawes. Distributed under the Boost Software License, Version 1.0. See accompanying file <a href="../../LICENSE_1_0.txt">LICENSE_1_0.txt</a> or copy at <a href="http://www.boost.org/LICENSE_1_0.txt">http://www.boost.org/LICENSE_1_0.txt</a>. </body> </html>