So the errorcheck object will be in a half-constructed state. That is,
int will be constructed, but the errorcheck object isn't, therefore the int's destructor will be called, but errorcheck's deconstructor will not.
The solution would therefore be to throw an intermediate object, like
From: Rob Stewart <stewart@sig.com> From: "Reece Dunn" <msclrhd@hotmail.com> the the
Trules from the C++ Templates book by David Vandervoorde and Nico Josuttis. This would then get around the throwing in a constructor problem.
Why not throw a new errorcheck object using a private ctor that stores but doesn't check the return value?
That would work (I realised an implementation after the post). But this is what I was trying to achieve using the copy constructor (and copy assignment), since that copies the object, but does not throw on failure. The errorcheck class now has a policy-based implementation, so it would look something like: template< typename ErrorStorage, typename ErrorMsgStorage > class errorcheck: public Storage, public MsgStorage { private: inline errorcheck( const Storage & s, const MsgStorage & ms ): Storage( s ), MsgStorage( ms ) { } public: inline errorcheck( typename Storage::error_type e ): Storage( e ), MsgStorage() { if( failed()) throw( errorcheck< Storage, MsgStorage >( *this, *this )); } }; which, IMHO, is more confusing than the straight throw( *this ), but does not use the copy constructor, relying instead of the fully constructed Storage and MsgStorage base classes. Regards, Reece _________________________________________________________________ Find a cheaper internet access deal - choose one to suit you. http://www.msn.co.uk/internetaccess