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Added MSVC workaround to value_initialized, as described by ticket #1217, proposed at the Boost Developers mailing list, and discussed with Fernando Cacciola.

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[SVN r39157]
This commit is contained in:
Niels Dekker 2007-09-07 17:17:09 +00:00
parent 3f72b10182
commit 55f3c351a3
1 changed files with 80 additions and 4 deletions
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84
include/boost/utility/value_init.hpp
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@ -1,10 +1,11 @@
// (C) 2002, Fernando Luis Cacciola Carballal.
// (C) Copyright 2002-2007, Fernando Luis Cacciola Carballal.
//
// Distributed under the Boost Software License, Version 1.0. (See
// accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
//
// 21 Ago 2002 (Created) Fernando Cacciola
// 07 Set 2007 (Worked around MSVC++ bug) Fernando Cacciola, Niels Dekker
//
#ifndef BOOST_UTILITY_VALUE_INIT_21AGO2002_HPP
#define BOOST_UTILITY_VALUE_INIT_21AGO2002_HPP
@ -13,6 +14,75 @@
#include <boost/type_traits/cv_traits.hpp>
#include <boost/detail/workaround.hpp>
#if BOOST_WORKAROUND(BOOST_MSVC, BOOST_TESTED_AT(1500) )
// Microsoft Visual C++ does not correctly support value initialization, as reported by
// Pavel Kuznetsov (MetaCommunications Engineering), 7/28/2005, Feedback ID 100744,
// Feedback Title: Value-initialization in new-expression
// https://connect.microsoft.com/VisualStudio/feedback/ViewFeedback.aspx?FeedbackID=100744
// The report was closed at 11/14/2006, and its status was set to "Closed (Won't Fix)".
// Luckily, even in the presence of this compiler bug, boost::value_initialized will still
// do its job correctly, when using the following workaround:
#define BOOST_UTILITY_VALUE_INIT_WORKAROUND
#endif
#ifdef BOOST_UTILITY_VALUE_INIT_WORKAROUND
#include <boost/aligned_storage.hpp>
#include <boost/type_traits/alignment_of.hpp>
#include <cstring>
#include <new>
namespace boost {
namespace vinit_detail {
template<class T>
class const_T_base
{
protected :
const_T_base()
{
std::memset(&x, 0, sizeof(x));
new (&x) T();
}
~const_T_base() { get().T::~T(); }
T & get() const
{
void const * ptr = &x;
return *static_cast<T*>(ptr);
}
private :
typename ::boost::aligned_storage<sizeof(T), ::boost::alignment_of<T>::value>::type x;
} ;
template<class T>
class non_const_T_base
{
protected :
non_const_T_base()
{
std::memset(&x, 0, sizeof(x));
new (&x) T();
}
~non_const_T_base() { get().T::~T(); }
T & get() const
{
void * ptr = &x;
return *static_cast<T*>(ptr);
}
private :
mutable typename ::boost::aligned_storage<sizeof(T), ::boost::alignment_of<T>::value>::type x;
} ;
#else
namespace boost {
namespace vinit_detail {
@ -23,20 +93,26 @@ class const_T_base
protected :
const_T_base() : x() {}
T & get() const { return x; }
private :
T x ;
} ;
template<class T>
struct non_const_T_base
class non_const_T_base
{
protected :
non_const_T_base() : x() {}
T & get() const { return x; }
private :
mutable T x ;
} ;
#endif
template<class T>
struct select_base
{
@ -57,9 +133,9 @@ class value_initialized : private vinit_detail::select_base<T>::type
value_initialized() {}
operator T&() const { return this->x ; }
operator T&() const { return this->get(); }
T& data() const { return this->x ; }
T& data() const { return this->get(); }
} ;