We have a class that contains a std::map. This class wants to provide its clients with iterators over just the values in the map, hiding the fact that there's a map under the covers at all. transform_iterator seems like just the ticket, and with Boost 1.31 we used these methods: typedef std::map<KEYTYPE, VALUETYPE> MapType; typedef boost::transform_iterator< boost::function<const MapType::mapped_type&(const MapType::value_type&)>, MapType::const_iterator > const_iterator; const_iterator begin() const { return boost::make_transform_iterator(mymap.begin(), boost::bind(&MapType::value_type::second, _1)); } const_iterator end() const { return boost::make_transform_iterator(mymap.end(), boost::bind(&MapType::value_type::second, _1)); } The above compiled cleanly, except when it caused a compiler ICE, and the instances that compile seem to run okay. Now we're trying to upgrade to Boost 1.32 -- I know, a little late in the 1.32 lifespan. The same code now produces an ominous warning (full text at end of message): c:/videobranch\boost\boost\function\function_template.hpp(111) : warning C4172: returning address of local variable or temporary When it finally gets around to mentioning a line number in our own source code, the indicated line is the return statement in the above begin() method. The reason I'm concerned is that when compiled with Boost 1.32, our program suffers mysterious crashes that it did not when compiled with Boost 1.31. :-( I don't *know* that this warning is related, but I thought it prudent to try to eliminate such warnings to see if that might help. I can't figure out what temporary is driving the warning, though. I tried factoring out our own code a couple of different ways without making the warning go away. Can you suggest anything? Platform: Microsoft Windows XP Pro Compiler: Microsoft Visual C++ .NET, aka 7.1 *** Message ends; what follows is Microsoft warning output *** cl /EHsc /I c:/videobranch/boost $FF Microsoft (R) 32-bit C/C++ Optimizing Compiler Version 13.10.3077 for 80x86 Copyright (C) Microsoft Corporation 1984-2002. All rights reserved. WrapMap.cpp c:/videobranch\boost\boost\function\function_template.hpp(111) : warning C4172: returning address of local variable or temporary c:/videobranch\boost\boost\function\function_template.hpp(109) : while compiling class-template member function 'const int boost::detail::function::function_obj_invoker1<FunctionObj,R,T0>::invoke (boost::detail::function::any_pointer,T0)' with [ FunctionObj=boost::_bi::bind_t<int,boost::_mfi::dm<int,std::pair<const std::string,int>>,boost::_bi::list1<boost::_bi::list_av_1<boost::arg<1>> ::B1>>, R=const int &, T0=const std::pair<const std::string,int> & ] c:/videobranch\boost\boost\function\function_template.hpp(482) : see reference to class template instantiation 'boost::detail::function::function_obj_invoker1<FunctionObj,R,T0>' being compiled with [ FunctionObj=boost::_bi::bind_t<int,boost::_mfi::dm<int,std::pair<const std::string,int>>,boost::_bi::list1<boost::_bi::list_av_1<boost::arg<1>> ::B1>>, R=const int &, T0=const std::pair<const std::string,int> & ] c:/videobranch\boost\boost\function\function_template.hpp(433) : see reference to function template instantiation 'void boost::function1<R,T0,Allocator>::assign_to<Functor>(FunctionObj,boost:: detail::function::function_obj_tag)' being compiled with [ R=const int &, T0=const std::pair<const std::string,int> &, Allocator=std::allocator<void>, Functor=boost::_bi::bind_t<int,boost::_mfi::dm<int,std::pair<const std::string,int>>,boost::_bi::list1<boost::_bi::list_av_1<boost::arg<1>> ::B1>>, FunctionObj=boost::_bi::bind_t<int,boost::_mfi::dm<int,std::pair<const std::string,int>>,boost::_bi::list1<boost::_bi::list_av_1<boost::arg<1>> ::B1>> ] c:/videobranch\boost\boost\function\function_template.hpp(289) : see reference to function template instantiation 'void boost::function1<R,T0,Allocator>::assign_to<Functor>(Functor)' being compiled with [ R=const int &, T0=const std::pair<const std::string,int> &, Allocator=std::allocator<void>, Functor=boost::_bi::bind_t<int,boost::_mfi::dm<int,std::pair<const std::string,int>>,boost::_bi::list1<boost::_bi::list_av_1<boost::arg<1>> ::B1>> ] c:/videobranch\boost\boost\function\function_template.hpp(649) : see reference to function template instantiation 'boost::function1<R,T0,Allocator>::function1<UnaryFunction>(Functor,boos t::enable_if_c<B,T>::type)' being compiled with [ R=const int &, T0=const std::pair<const std::string,int> &, Allocator=std::allocator<void>, UnaryFunction=boost::_bi::bind_t<int,boost::_mfi::dm<int,std::pair<const std::string,int>>,boost::_bi::list1<boost::_bi::list_av_1<boost::arg<1>> ::B1>>, Functor=boost::_bi::bind_t<int,boost::_mfi::dm<int,std::pair<const std::string,int>>,boost::_bi::list1<boost::_bi::list_av_1<boost::arg<1>> ::B1>>, B=true, T=int ] c:/videobranch\boost\boost\iterator\transform_iterator.hpp(130) : see reference to function template instantiation 'boost::function<Signature>::function<UnaryFunction>(Functor,boost::enab le_if_c<B,T>::type)' being compiled with [ Signature=const std::map<std::string,int>::mapped_type &(const std::map<std::string,int>::value_type &), UnaryFunction=boost::_bi::bind_t<int,boost::_mfi::dm<int,std::pair<const std::string,int>>,boost::_bi::list1<boost::_bi::list_av_1<boost::arg<1>> ::B1>>, Functor=boost::_bi::bind_t<int,boost::_mfi::dm<int,std::pair<const std::string,int>>,boost::_bi::list1<boost::_bi::list_av_1<boost::arg<1>> ::B1>>, B=true, T=int ] WrapMap.cpp(20) : see reference to function template instantiation 'boost::transform_iterator<UnaryFunction,Iterator>::transform_iterator<b oost::_bi::bind_t<R,F,L>,std::_Tree<_Traits>::const_iterator,boost::use_ default,boost::use_default>(const boost::transform_iterator<boost::_bi::bind_t<R,F,L>,Iterator,Reference,V alue> &,boost::iterators::enabled<__formal>::base<T>::type *)' being compiled with [ UnaryFunction=boost::function<const std::map<std::string,int>::mapped_type &(const std::map<std::string,int>::value_type &)>, Iterator=std::map<std::string,int>::const_iterator, R=int, F=boost::_mfi::dm<int,std::pair<const std::string,int>>, L=boost::_bi::list1<boost::_bi::list_av_1<boost::arg<1>>::B1>, _Traits=std::_Tmap_traits<std::string,int,std::less<std::string>,std::al locator<std::pair<const std::string,int>>,false>, Reference=boost::use_default, Value=boost::use_default, __formal=true, T=boost::detail::enable_type ]