Is it really a bug? AFAIK, the compiler is ordered to apply template function "distance" on two members of the class. The function is const, so the members must be const, in this case its final type will be "const char * const". So the template deduced automatically will have the type "const char * const" as "InputIterator", which is not a valid input iterator, as it may not step forward or backward.
There is a rule in template type deduction that the final const gets dropped: Given: template <class T> foo(T z); Then: int i; const int j; foo(i); // calls foo<int> foo(j); // also calls foo<int> This is to ensure consistency with non-template function calls, and also makes sense once you realise that foo<int> and foo<const int> would have the same signature and type anyway. John.