1 #ifndef BOOST_WEAK_PTR_HPP_INCLUDED
2 #define BOOST_WEAK_PTR_HPP_INCLUDED
7 // Copyright (c) 2001, 2002, 2003 Peter Dimov
9 // Distributed under the Boost Software License, Version 1.0. (See
10 // accompanying file LICENSE_1_0.txt or copy at
11 // http://www.boost.org/LICENSE_1_0.txt)
13 // See http://www.boost.org/libs/smart_ptr/weak_ptr.htm for documentation.
16 #include <memory> // boost.TR1 include order fix
17 #include <boost/detail/shared_count.hpp>
18 #include <boost/shared_ptr.hpp>
20 #ifdef BOOST_MSVC // moved here to work around VC++ compiler crash
21 # pragma warning(push)
22 # pragma warning(disable:4284) // odd return type for operator->
28 template<class T> class weak_ptr
32 // Borland 5.5.1 specific workarounds
33 typedef weak_ptr<T> this_type;
37 typedef T element_type;
39 weak_ptr(): px(0), pn() // never throws in 1.30+
43 // generated copy constructor, assignment, destructor are fine
47 // The "obvious" converting constructor implementation:
50 // weak_ptr(weak_ptr<Y> const & r): px(r.px), pn(r.pn) // never throws
54 // has a serious problem.
56 // r.px may already have been invalidated. The px(r.px)
57 // conversion may require access to *r.px (virtual inheritance).
59 // It is not possible to avoid spurious access violations since
60 // in multithreaded programs r.px may be invalidated at any point.
64 #if !defined( BOOST_SP_NO_SP_CONVERTIBLE )
66 weak_ptr( weak_ptr<Y> const & r, typename detail::sp_enable_if_convertible<Y,T>::type = detail::sp_empty() )
70 weak_ptr( weak_ptr<Y> const & r )
73 : pn(r.pn) // never throws
79 #if !defined( BOOST_SP_NO_SP_CONVERTIBLE )
81 weak_ptr( shared_ptr<Y> const & r, typename detail::sp_enable_if_convertible<Y,T>::type = detail::sp_empty() )
85 weak_ptr( shared_ptr<Y> const & r )
88 : px( r.px ), pn( r.pn ) // never throws
92 #if !defined(BOOST_MSVC) || (BOOST_MSVC >= 1300)
95 weak_ptr & operator=(weak_ptr<Y> const & r) // never throws
103 weak_ptr & operator=(shared_ptr<Y> const & r) // never throws
112 shared_ptr<T> lock() const // never throws
114 return shared_ptr<element_type>( *this, boost::detail::sp_nothrow_tag() );
117 long use_count() const // never throws
119 return pn.use_count();
122 bool expired() const // never throws
124 return pn.use_count() == 0;
127 void reset() // never throws in 1.30+
129 this_type().swap(*this);
132 void swap(this_type & other) // never throws
134 std::swap(px, other.px);
138 void _internal_assign(T * px2, boost::detail::shared_count const & pn2)
144 template<class Y> bool _internal_less(weak_ptr<Y> const & rhs) const
149 // Tasteless as this may seem, making all members public allows member templates
150 // to work in the absence of member template friends. (Matthew Langston)
152 #ifndef BOOST_NO_MEMBER_TEMPLATE_FRIENDS
156 template<class Y> friend class weak_ptr;
157 template<class Y> friend class shared_ptr;
161 T * px; // contained pointer
162 boost::detail::weak_count pn; // reference counter
166 template<class T, class U> inline bool operator<(weak_ptr<T> const & a, weak_ptr<U> const & b)
168 return a._internal_less(b);
171 template<class T> void swap(weak_ptr<T> & a, weak_ptr<T> & b)
179 # pragma warning(pop)
182 #endif // #ifndef BOOST_WEAK_PTR_HPP_INCLUDED