variadic templates - ambiguous call

Question

The following code compiles in both gcc 4.7.2 and MSVC-11.0:

template 
void foo(T bar) {}

template 
vo         


        

Answer 1

This is considered a defect in the current standard. Even the standard itself relies on non-variadic templates to be partially ordered before variadic ones in the specification of std::common_type:

§20.9.7.6 [meta.trans.other] p3

The nested typedef common_type::type shall be defined as follows:

template  struct common_type;

template 
struct common_type {
  typedef T type;
};

template 
struct common_type {
  typedef decltype(true ? declval() : declval()) type;
};

template 
struct common_type {
  typedef typename common_type::type, V...>::type type;
};

Specifically common_type vs common_type.