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Fixed (hopefully) conflict between boost::base_from_member's C++11 constructor template and the automatically defined non-template copy- and/or move-constructors.

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[SVN r77046]
This commit is contained in:
Daryle Walker 2012-02-17 01:55:33 +00:00
parent d6cb9a9176
commit 0db9276e8c
2 changed files with 75 additions and 13 deletions
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24
base_from_member.html
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@ -174,16 +174,18 @@ value of zero if it is omitted. The class template has a protected
data member called <var>member</var> that the derived class can use
for later base classes (or itself).</p>
<p>If the variadic template arguments and r-value reference features of C++2011
are present, there will be a single constructor template. It implements
&quot;perfect forwarding&quot; to the best constructor call of
<code>member</code> (if any). The constructor template is marked both
<code>constexpr</code> and <code>explicit</code>. The former will be ignored
if the corresponding inner constructor call (of <code>member</code>) does not
have the marker. The latter binds the other way; always taking effect, even
when the inner constructor call does not have the marker. The constructor
template propagates the <code>noexcept</code> status of the inner constructor
call.</p>
<p>If the appropriate features of C++2011 are present, there will be a single
constructor template. It implements &quot;perfect forwarding&quot; to the best
constructor call of <code>member</code> (if any). The constructor template is
marked both <code>constexpr</code> and <code>explicit</code>. The former will
be ignored if the corresponding inner constructor call (of <code>member</code>)
does not have the marker. The latter binds the other way; always taking
effect, even when the inner constructor call does not have the marker. The
constructor template propagates the <code>noexcept</code> status of the inner
constructor call. (The constructor template has a trailing parameter with a
default value that disables the template when its signature is too close to the
signatures of the automatically-defined non-template copy- and/or
move-constructors of <code>base_from_member</code>.)</p>
<p>On earlier-standard compilers, there is a default constructor and several
constructor member templates. These constructor templates can take as many
@ -385,7 +387,7 @@ a constructor call but <code>std::nullptr_t</code> cannot.)</p>
<hr>
<p>Revised: 11 February 2012</p>
<p>Revised: 16 February 2012</p>
<p>Copyright 2001, 2003, 2004, 2012 Daryle Walker. Use, modification, and distribution
are subject to the Boost Software License, Version 1.0. (See accompanying

64
include/boost/utility/base_from_member.hpp
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@ -15,6 +15,10 @@
#include <boost/preprocessor/repetition/enum_binary_params.hpp>
#include <boost/preprocessor/repetition/enum_params.hpp>
#include <boost/preprocessor/repetition/repeat_from_to.hpp>
#include <boost/type_traits/is_same.hpp>
#include <boost/type_traits/remove_cv.hpp>
#include <boost/type_traits/remove_reference.hpp>
#include <boost/utility/enable_if.hpp>
// Base-from-member arity configuration macro ------------------------------//
@ -54,6 +58,59 @@
namespace boost
{
namespace detail
{
// Type-unmarking class template -------------------------------------------//
// Type-trait to get the raw type, i.e. the type without top-level reference nor
// cv-qualification, from a type expression. Mainly for function arguments, any
// reference part is stripped first.
// Contributed by Daryle Walker
template < typename T >
struct remove_cv_ref
{
typedef typename ::boost::remove_cv<typename
::boost::remove_reference<T>::type>::type type;
}; // boost::detail::remove_cv_ref
// Unmarked-type comparison class template ---------------------------------//
// Type-trait to check if two type expressions have the same raw type.
// Contributed by Daryle Walker, based on a work-around by Luc Danton
template < typename T, typename U >
struct is_related
: public ::boost::is_same<
typename ::boost::detail::remove_cv_ref<T>::type,
typename ::boost::detail::remove_cv_ref<U>::type >
{};
// Enable-if-on-unidentical-unmarked-type class template -------------------//
// Enable-if on the first two type expressions NOT having the same raw type.
// Contributed by Daryle Walker, based on a work-around by Luc Danton
#ifndef BOOST_NO_VARIADIC_TEMPLATES
template<typename ...T>
struct enable_if_unrelated
: public ::boost::enable_if_c<true>
{};
template<typename T, typename U, typename ...U2>
struct enable_if_unrelated<T, U, U2...>
: public ::boost::disable_if< ::boost::detail::is_related<T, U> >
{};
#endif
} // namespace boost::detail
// Base-from-member class template -----------------------------------------//
// Helper to initialize a base object so a derived class can use this
@ -69,8 +126,11 @@ class base_from_member
protected:
MemberType member;
#if defined(BOOST_HAS_RVALUE_REFS) && defined(BOOST_HAS_VARIADIC_TMPL)
template <typename ...T>
#if !defined(BOOST_NO_RVALUE_REFERENCES) && \
!defined(BOOST_NO_VARIADIC_TEMPLATES) && \
!defined(BOOST_NO_FUNCTION_TEMPLATE_DEFAULT_ARGS)
template <typename ...T, typename EnableIf = typename
::boost::detail::enable_if_unrelated<base_from_member, T...>::type>
explicit BOOST_CONSTEXPR base_from_member( T&& ...x )
BOOST_NOEXCEPT_IF( BOOST_NOEXCEPT_EXPR(::new ((void*) 0) MemberType(
static_cast<T&&>(x)... )) ) // no std::is_nothrow_constructible...