I wanted to say that the original implementation (http://www.pdimov.com/cpp/shared_count_x86_exp2.hpp) has a bug. Take a look at it please.
The site seems to be inaccessible. Are you sure that its lock() doesn't call InterlockedCompareExchange when it sees not expired refcount?
Just to make sure, I paste here the code: ----------------------------------- #ifndef BOOST_DETAIL_SHARED_COUNT_HPP_INCLUDED #define BOOST_DETAIL_SHARED_COUNT_HPP_INCLUDED #if defined(_MSC_VER) && (_MSC_VER >= 1020) # pragma once #endif // // detail/shared_count_x86_exp.hpp // // An experimental version of shared_count.hpp that uses x86-32 // atomic instructions (the Interlocked* family) // // Copyright (c) 2001, 2002, 2003 Peter Dimov and Multi Media Ltd. // // Permission to copy, use, modify, sell and distribute this software // is granted provided this copyright notice appears in all copies. // This software is provided "as is" without express or implied // warranty, and with no claim as to its suitability for any purpose. // #include <boost/config.hpp> #if defined(BOOST_SP_USE_STD_ALLOCATOR) && defined(BOOST_SP_USE_QUICK_ALLOCATOR) # error BOOST_SP_USE_STD_ALLOCATOR and BOOST_SP_USE_QUICK_ALLOCATOR are incompatible. #endif #include <boost/checked_delete.hpp> #include <boost/throw_exception.hpp> #if defined(BOOST_SP_USE_QUICK_ALLOCATOR) #include <boost/detail/quick_allocator.hpp> #endif #include <memory> // std::auto_ptr, std::allocator #include <functional> // std::less #include <exception> // std::exception #include <new> // std::bad_alloc #include <typeinfo> // std::type_info in get_deleter #include <cstddef> // std::size_t #ifdef __BORLANDC__ # pragma warn -8026 // Functions with excep. spec. are not expanded inline # pragma warn -8027 // Functions containing try are not expanded inline #endif // Interlocked* extern "C" { long __cdecl _InterlockedIncrement(long volatile * destination); long __cdecl _InterlockedDecrement(long volatile * destination); long __cdecl _InterlockedCompareExchange(long volatile * destination, long exchange, long comparand); } #pragma intrinsic(_InterlockedIncrement) #pragma intrinsic(_InterlockedDecrement) #pragma intrinsic(_InterlockedCompareExchange) namespace boost { // Debug hooks #if defined(BOOST_SP_ENABLE_DEBUG_HOOKS) void sp_scalar_constructor_hook(void * px, std::size_t size, void * pn); void sp_array_constructor_hook(void * px); void sp_scalar_destructor_hook(void * px, std::size_t size, void * pn); void sp_array_destructor_hook(void * px); #endif // The standard library that comes with Borland C++ 5.5.1 // defines std::exception and its members as having C calling // convention (-pc). When the definition of bad_weak_ptr // is compiled with -ps, the compiler issues an error. // Hence, the temporary #pragma option -pc below. The version // check is deliberately conservative. #if defined(__BORLANDC__) && __BORLANDC__ == 0x551 # pragma option push -pc #endif class bad_weak_ptr: public std::exception { public: virtual char const * what() const throw() { return "boost::bad_weak_ptr"; } }; #if defined(__BORLANDC__) && __BORLANDC__ == 0x551 # pragma option pop #endif namespace detail { // inline long atomic_increment(long volatile & value) { return _InterlockedIncrement(&value); } inline long atomic_decrement(long volatile & value) { return _InterlockedDecrement(&value); } inline long atomic_read(long volatile const & value) { return value; } inline long atomic_conditional_increment(long volatile & value) { for(;;) { long tmp = value; if(tmp == 0) return 0; if(_InterlockedCompareExchange(&value, tmp + 1, tmp) == tmp) return tmp + 1; } } // class sp_counted_base { public: sp_counted_base(): use_count_(1), weak_count_(1) { } virtual ~sp_counted_base() // nothrow { } // dispose() is called when use_count_ drops to zero, to release // the resources managed by *this. virtual void dispose() = 0; // nothrow // destruct() is called when weak_count_ drops to zero. virtual void destruct() // nothrow { delete this; } virtual void * get_deleter(std::type_info const & ti) = 0; void add_ref_copy() { atomic_increment(use_count_); } void add_ref_lock() { if(atomic_conditional_increment(use_count_) == 0) boost::throw_exception(boost::bad_weak_ptr()); } void release() // nothrow { if(atomic_decrement(use_count_) == 0) { dispose(); weak_release(); } } void weak_add_ref() // nothrow { atomic_increment(weak_count_); } void weak_release() // nothrow { if(atomic_decrement(weak_count_) == 0) { destruct(); } } long use_count() const // nothrow { return atomic_read(use_count_); } private: sp_counted_base(sp_counted_base const &); sp_counted_base & operator= (sp_counted_base const &); long use_count_; long weak_count_; // weak_count + (use_count == 0) }; #if defined(BOOST_SP_ENABLE_DEBUG_HOOKS) template<class T> void cbi_call_constructor_hook(sp_counted_base * pn, T * px, checked_deleter<T> const &, int) { boost::sp_scalar_constructor_hook(px, sizeof(T), pn); } template<class T> void cbi_call_constructor_hook(sp_counted_base *, T * px, checked_array_deleter<T> const &, int) { boost::sp_array_constructor_hook(px); } template<class P, class D> void cbi_call_constructor_hook(sp_counted_base *, P const &, D const &, long) { } template<class T> void cbi_call_destructor_hook(sp_counted_base * pn, T * px, checked_deleter<T> const &, int) { boost::sp_scalar_destructor_hook(px, sizeof(T), pn); } template<class T> void cbi_call_destructor_hook(sp_counted_base *, T * px, checked_array_deleter<T> const &, int) { boost::sp_array_destructor_hook(px); } template<class P, class D> void cbi_call_destructor_hook(sp_counted_base *, P const &, D const &, long) { } #endif // // Borland's Codeguard trips up over the -Vx- option here: // #ifdef __CODEGUARD__ # pragma option push -Vx- #endif template<class P, class D> class sp_counted_base_impl: public sp_counted_base { private: P ptr; // copy constructor must not throw D del; // copy constructor must not throw sp_counted_base_impl(sp_counted_base_impl const &); sp_counted_base_impl & operator= (sp_counted_base_impl const &); typedef sp_counted_base_impl<P, D> this_type; public: // pre: initial_use_count <= initial_weak_count, d(p) must not throw sp_counted_base_impl(P p, D d): ptr(p), del(d) { #if defined(BOOST_SP_ENABLE_DEBUG_HOOKS) detail::cbi_call_constructor_hook(this, p, d, 0); #endif } virtual void dispose() // nothrow { #if defined(BOOST_SP_ENABLE_DEBUG_HOOKS) detail::cbi_call_destructor_hook(this, ptr, del, 0); #endif del(ptr); } virtual void * get_deleter(std::type_info const & ti) { return ti == typeid(D)? &del: 0; } #if defined(BOOST_SP_USE_STD_ALLOCATOR) void * operator new(std::size_t) { return std::allocator<this_type>().allocate(1, static_cast<this_type *>(0)); } void operator delete(void * p) { std::allocator<this_type>().deallocate(static_cast<this_type *>(p), 1); } #endif #if defined(BOOST_SP_USE_QUICK_ALLOCATOR) void * operator new(std::size_t) { return quick_allocator<this_type>::alloc(); } void operator delete(void * p) { quick_allocator<this_type>::dealloc(p); } #endif }; #if defined(BOOST_SP_ENABLE_DEBUG_HOOKS) int const shared_count_id = 0x2C35F101; int const weak_count_id = 0x298C38A4; #endif class weak_count; class shared_count { private: sp_counted_base * pi_; #if defined(BOOST_SP_ENABLE_DEBUG_HOOKS) int id_; #endif friend class weak_count; public: shared_count(): pi_(0) // nothrow #if defined(BOOST_SP_ENABLE_DEBUG_HOOKS) , id_(shared_count_id) #endif { } template<class P, class D> shared_count(P p, D d): pi_(0) #if defined(BOOST_SP_ENABLE_DEBUG_HOOKS) , id_(shared_count_id) #endif { #ifndef BOOST_NO_EXCEPTIONS try { pi_ = new sp_counted_base_impl<P, D>(p, d); } catch(...) { d(p); // delete p throw; } #else pi_ = new sp_counted_base_impl<P, D>(p, d); if(pi_ == 0) { d(p); // delete p boost::throw_exception(std::bad_alloc()); } #endif } #ifndef BOOST_NO_AUTO_PTR // auto_ptr<Y> is special cased to provide the strong guarantee template<class Y> explicit shared_count(std::auto_ptr<Y> & r): pi_(new sp_counted_base_impl< Y *, checked_deleter<Y> >(r.get(), checked_deleter<Y>())) #if defined(BOOST_SP_ENABLE_DEBUG_HOOKS) , id_(shared_count_id) #endif { r.release(); } #endif ~shared_count() // nothrow { if(pi_ != 0) pi_->release(); #if defined(BOOST_SP_ENABLE_DEBUG_HOOKS) id_ = 0; #endif } shared_count(shared_count const & r): pi_(r.pi_) // nothrow #if defined(BOOST_SP_ENABLE_DEBUG_HOOKS) , id_(shared_count_id) #endif { if(pi_ != 0) pi_->add_ref_copy(); } explicit shared_count(weak_count const & r); // throws bad_weak_ptr when r.use_count() == 0 shared_count & operator= (shared_count const & r) // nothrow { sp_counted_base * tmp = r.pi_; if(tmp != 0) tmp->add_ref_copy(); if(pi_ != 0) pi_->release(); pi_ = tmp; return *this; } void swap(shared_count & r) // nothrow { sp_counted_base * tmp = r.pi_; r.pi_ = pi_; pi_ = tmp; } long use_count() const // nothrow { return pi_ != 0? pi_->use_count(): 0; } bool unique() const // nothrow { return use_count() == 1; } friend inline bool operator==(shared_count const & a, shared_count const & b) { return a.pi_ == b.pi_; } friend inline bool operator<(shared_count const & a, shared_count const & b) { return std::less<sp_counted_base *>()(a.pi_, b.pi_); } void * get_deleter(std::type_info const & ti) const { return pi_? pi_->get_deleter(ti): 0; } }; #ifdef __CODEGUARD__ # pragma option pop #endif class weak_count { private: sp_counted_base * pi_; #if defined(BOOST_SP_ENABLE_DEBUG_HOOKS) int id_; #endif friend class shared_count; public: weak_count(): pi_(0) // nothrow #if defined(BOOST_SP_ENABLE_DEBUG_HOOKS) , id_(weak_count_id) #endif { } weak_count(shared_count const & r): pi_(r.pi_) // nothrow #if defined(BOOST_SP_ENABLE_DEBUG_HOOKS) , id_(shared_count_id) #endif { if(pi_ != 0) pi_->weak_add_ref(); } weak_count(weak_count const & r): pi_(r.pi_) // nothrow #if defined(BOOST_SP_ENABLE_DEBUG_HOOKS) , id_(shared_count_id) #endif { if(pi_ != 0) pi_->weak_add_ref(); } ~weak_count() // nothrow { if(pi_ != 0) pi_->weak_release(); #if defined(BOOST_SP_ENABLE_DEBUG_HOOKS) id_ = 0; #endif } weak_count & operator= (shared_count const & r) // nothrow { sp_counted_base * tmp = r.pi_; if(tmp != 0) tmp->weak_add_ref(); if(pi_ != 0) pi_->weak_release(); pi_ = tmp; return *this; } weak_count & operator= (weak_count const & r) // nothrow { sp_counted_base * tmp = r.pi_; if(tmp != 0) tmp->weak_add_ref(); if(pi_ != 0) pi_->weak_release(); pi_ = tmp; return *this; } void swap(weak_count & r) // nothrow { sp_counted_base * tmp = r.pi_; r.pi_ = pi_; pi_ = tmp; } long use_count() const // nothrow { return pi_ != 0? pi_->use_count(): 0; } friend inline bool operator==(weak_count const & a, weak_count const & b) { return a.pi_ == b.pi_; } friend inline bool operator<(weak_count const & a, weak_count const & b) { return std::less<sp_counted_base *>()(a.pi_, b.pi_); } }; inline shared_count::shared_count(weak_count const & r): pi_(r.pi_) #if defined(BOOST_SP_ENABLE_DEBUG_HOOKS) , id_(shared_count_id) #endif { if(pi_ != 0) { pi_->add_ref_lock(); } else { boost::throw_exception(boost::bad_weak_ptr()); } } } // namespace detail } // namespace boost #ifdef __BORLANDC__ # pragma warn .8027 // Functions containing try are not expanded inline # pragma warn .8026 // Functions with excep. spec. are not expanded inline #endif #endif // #ifndef BOOST_DETAIL_SHARED_COUNT_HPP_INCLUDED ------------------------- -- John Torjo -- john@torjo.com Contributing editor, C/C++ Users Journal -- "Win32 GUI Generics" -- generics & GUI do mix, after all -- http://www.torjo.com/win32gui/ -- v1.4 - save_dlg - true binding of your data to UI controls! + easily add validation rules (win32gui/examples/smart_dlg)