I'm using the current Boost library on Microsoft Visual Studio 2005. I'm getting a warning on line 121 of transform_iterator.hpp, complaining "returning address of local variable or temporary". The line in question is the body of this function:
typename super_t::reference dereference() const { return m_f(*this->base()); }
My m_f supplied to the template is ordinary enough; it returns a value.
Is your m_f a function object that uses result_of protocol to declare its return value? It may be that while its operator() returns a value, its result<> is telling transform_iterator that it returns a reference. For example, if its result<> looks like this: template <typename> struct result; template <typename F, typename T> struct result<F(T)> { typedef T type; }; then transform iterator will deduce its return type to be a reference: typedef typename ia_dflt_help< Reference , result_of<UnaryFunc(typename std::iterator_traits<Iterator>::reference)> >::type reference; and it will use this as the return type of operator*. Hence the warning. Instead, you need to declare result<> like this: template <typename> struct result; template <typename F, typename T> struct result<F(const T&)> { typedef T type; }; (and possibly add a non-const reference version if necessary). Regards, Nate.