I have a class that override two different new operators. This give an "ambiguous call to overloaded function" error message in VisualC++2005. Example on code that will give error: class A { public: void* operator new(std::size_t); void* operator new(std::size_t, void*); }; int _tmain(int argc, _TCHAR* argv[]) { boost::has_new_operator<A>(); return 0; } I think that the has_new_operator could be updated with a new check_sig3 test. Where the new(std::size_t, void*) is moved to the new check_sig3. The serialization code use the has_new_operator to decide if it should call T::new or ::new. But what should happen if only the operation new for arrays is overridden? If T::new function only should be called when the operator new(size_t) is overridden then the has_new_operator function should be split into three different functions (ex. has_new_operator, has_new_operator_array and has_new_operator_placement)? - Runar