Hi list, I was in the need for a shared_from_this() in my constructor, so I chose this implementation for my class. Apart from the header being there and one mailing list thread, there's nothing that points to the existence of this header. Since we want to keep compatibility with Boost 1.38, I tried to backport the enable_shared_from_this2 class to that version. I was wondering why the weak_ptr::_empty() method was added to the weak_ptr API and why weak_ptr::expired() was not used instead ? I tried to emulate the same behavior by adding a 'bool' to the enable_shared_from_this2 class. Which works for my tests, but is there a pitfall to that solution ? Could I just replace this logic with weak_this_.expired() ? diff --git a/rtt/internal/enable_shared_from_this2.hpp b/rtt/internal/enable_shared_from_this2.hpp index a5bfcff..cb659f0 100644 --- a/rtt/internal/enable_shared_from_this2.hpp +++ b/rtt/internal/enable_shared_from_this2.hpp @@ -53,11 +53,13 @@ template< class T > class enable_shared_from_this2 { protected: - enable_shared_from_this2() + enable_shared_from_this2() : weak_init(false) { } - enable_shared_from_this2( enable_shared_from_this2 const & ) + // note: the copy constructor and operator= don't do anything, ie, they don't copy + // refcount status from the other object. + enable_shared_from_this2( enable_shared_from_this2 const & ) : weak_init(false) { } @@ -75,6 +77,7 @@ private: mutable weak_ptr<T> weak_this_; mutable shared_ptr<T> shared_this_; + mutable bool weak_init; // we deviate from the boost 1.40 implementation because weak_this_._empty() is not available in older versions. public: @@ -94,10 +97,11 @@ private: void init_weak_once() const { - if( weak_this_._empty() ) + if( !weak_init ) { shared_this_.reset( static_cast< T* >( 0 ), detail::esft2_deleter_wrapper() ); weak_this_ = shared_this_; + weak_init = true; } } @@ -111,6 +115,7 @@ public: // actually private, but avoids compiler template friendship issues if( weak_this_.use_count() == 0 ) { weak_this_ = shared_ptr<T>( *ppx, py ); + weak_init = true; } else if( shared_this_.use_count() != 0 ) { Thanks for any feedback, Peter