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Added convenience class initialized_value, as announced at http://article.gmane.org/gmane.comp.lib.boost.devel/169833

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[SVN r42815]
This commit is contained in:
Niels Dekker 2008-01-16 09:35:12 +00:00
parent 9ed68b8321
commit 8ce58b1675
1 changed files with 18 additions and 17 deletions
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35
include/boost/utility/value_init.hpp
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@ -1,31 +1,20 @@
// (C) Copyright 2002-2007, Fernando Luis Cacciola Carballal. // (C) Copyright 2002-2008, Fernando Luis Cacciola Carballal.
// //
// Distributed under the Boost Software License, Version 1.0. (See // Distributed under the Boost Software License, Version 1.0. (See
// accompanying file LICENSE_1_0.txt or copy at // accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt) // http://www.boost.org/LICENSE_1_0.txt)
// //
// 21 Ago 2002 (Created) Fernando Cacciola // 21 Ago 2002 (Created) Fernando Cacciola
// 24 Dec 2007 (Refactored and worked around various compiler bugs) Fernando Cacciola, Niels Dekker // 16 Jan 2008 (Worked around compiler bugs, added initialized_value) Fernando Cacciola, Niels Dekker
// //
#ifndef BOOST_UTILITY_VALUE_INIT_21AGO2002_HPP #ifndef BOOST_UTILITY_VALUE_INIT_21AGO2002_HPP
#define BOOST_UTILITY_VALUE_INIT_21AGO2002_HPP #define BOOST_UTILITY_VALUE_INIT_21AGO2002_HPP
// Note: The implementation of boost::value_initialized had to deal with the // Note: The implementation of boost::value_initialized had to deal with the
// fact that various compilers haven't fully implemented value-initialization: // fact that various compilers haven't fully implemented value-initialization.
// Microsoft Feedback ID 100744 - Value-initialization in new-expression // The constructor of boost::value_initialized<T> works around these compiler
// Reported by Pavel Kuznetsov (MetaCommunications Engineering), 2005-07-28 // issues, by clearing the bytes of T, before constructing the T object it
// https://connect.microsoft.com/VisualStudio/feedback/ViewFeedback.aspx?FeedbackID=100744 // contains. More details on these issues are at libs/utility/value_init.htm
// GCC Bug 30111 - Value-initialization of POD base class doesn't initialize members
// Reported by Jonathan Wakely, 2006-12-07
// http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30111
// GCC Bug 33916 - Default constructor fails to initialize array members
// Reported by Michael Elizabeth Chastain, 2007-10-26
// http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33916
// Borland Report 51854 - Value-initialization: POD struct should be zero-initialized
// Reported by Niels Dekker (LKEB, Leiden University Medical Center), 2007-11-09
// http://qc.codegear.com/wc/qcmain.aspx?d=51854
// The constructor of boost::value_initialized<T> works around these issues, by
// clearing the bytes of T, before constructing the T object it contains.
#include <boost/aligned_storage.hpp> #include <boost/aligned_storage.hpp>
#include <boost/detail/workaround.hpp> #include <boost/detail/workaround.hpp>
@ -110,6 +99,18 @@ T& get ( value_initialized<T>& x )
return x.data() ; return x.data() ;
} }
class initialized_value
{
public :
template <class T> operator T() const
{
return get( value_initialized<T>() );
}
};
} // namespace boost } // namespace boost