Question

By C++11 standard std::is_base_of<B, D> must return true if D is derived from B or if both are the same non-union class. But in VC++ 2010 stl implementation template return true if the type B is a ONLY base class of the type D! Is it a bug ?

At http://msdn.microsoft.com/en-us/library/bb982243(v=vs.100).aspx page in example section

std::is_base_of<base, base> == true

but this does not correspond VC++2010 STL implementation. Although it is consistent with the requirement of the C++11 standard. Where is a bug ?

Answer 1

is_base_of<int, int>::value evaluates to false (your comment indicates that this is the actual question you have) because is_base_of<>::value can evaluate to true only if the template parameters are class types. The C++11 standard’s Table 51 – Type relationship predicates (C++ 20.9.6 “Relationships between types”) defines is_base_type<> to evaluate to true if and only if (emphasis added):

Base is a base class of Derived without regard to cv-qualifiers or Base and Derived are not unions and name the same class type without regard to cv-qualifiers

The C++11 standard even has the following as one of its examples (C++11 20.9.6/3):

is_base_of<int, int>::value // false