template<class T> void swap_impl(T& left, T& right) { using std::swap; swap(left,right); // <-- Some compilers don't do ADL here! }
Steven Watanabe wrote:
There's a config macro |BOOST_FUNCTION_SCOPE_USING_DECLARATION_BREAKS_ADL|
Thanks! Interestingly, the macro is not defined for MSVC 7.1. And I'm not sure if it should, because for MSVC 7.1, a function scope using-declaration doesn't /always/ break ADL. But it definitely breaks ADL within the current boost_swap_impl::swap_impl<T> function.
Does it help to a) using namespace std; or b) put the using in the namespace rather than in the function
Yes it does!!! :-) Workaround "a" does the job! I tested locally, for msvc-9.0, msvc-7.1, and borland-5.82. Current SVN version of boost::swap: - msvc-9.0 passes all tests - msvc-7.1 fails on specialized_in_global, specialized_in_other - borland-5.82 fails on specialized_in_global, specialized_in_other, and swap_arrays Workaround a) "using namespace std;", instead of "using std::swap;", within the boost_swap_impl::swap_impl<T> function: - msvc-9.0 passes all tests - msvc-7.1 passes all tests - borland-5.82 fails /only/ on swap_arrays Workaround b) putting "using std::swap;" in the boost_swap_impl namespace rather than in the boost_swap_impl::swap_impl<T> function: - msvc-9.0 passes all tests - msvc-7.1 passes all tests - borland-5.82 passes specialized_in_other, but it still fails on specialized_in_global and swap_arrays. Do you think it would be okay to just apply workaround "a", as attached hereby? I mean, would it harm for other toolsets to have "using namespace std;" within the boost_swap_impl::swap_impl function? I'd rather not use BOOST_WORKAROUND (unless really necessary!), because it would be harder to maintain, and I'd rather not have the semantics of boost::swap differ from one compiler to another.
Anyway, I think we should add unit tests for std types! Definitely.
So I just added 7 tests, testing boost::swap on various types that have std as associated namespace: std_bitset.cpp tests swapping std::bitset<T>. std_dateorder.cpp tests swapping the enum std::time_base::dateorder, std_string.cpp tests swapping std::string. std_typeinfo_ptr.cpp tests swapping typeinfo pointers. std_vector_of_boost.cpp tests swapping a vector of boost types. std_vector_of_global.cpp tests swapping a vector of types from the global namespace. std_vector_of_other.cpp tests swapping a vector of types from another namespace. I think each of them /might/ independently fail, depending on compiler bugs or (possibly) boost::swap utility bugs. The code is very much based upon the original tests by Joseph. Please have a look: http://svn.boost.org/trac/boost/changeset/47943 Kind regards, Niels