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// (C) Copyright Daniel Frey and Robert Ramey 2009.
// (C) Copyright Balint Cserni 2017
// Use, modification and distribution are subject to the Boost Software License,
// Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt).
//
// See http://www.boost.org/libs/type_traits for most recent version including documentation.
#ifndef BOOST_TT_IS_VIRTUAL_BASE_OF_HPP_INCLUDED
#define BOOST_TT_IS_VIRTUAL_BASE_OF_HPP_INCLUDED
#include <boost/type_traits/is_base_of.hpp>
#include <boost/type_traits/is_same.hpp>
#include <boost/type_traits/make_void.hpp>
#include <utility>
namespace boost {
namespace detail {
#ifdef BOOST_MSVC
#pragma warning( push )
#pragma warning( disable : 4584 4250 4594)
#elif defined(__GNUC__) && (__GNUC__ >= 4)
#pragma GCC system_header
#endif
#if !defined(BOOST_NO_SFINAE_EXPR) && !defined(BOOST_NO_CXX11_FUNCTION_TEMPLATE_DEFAULT_ARGS) && !defined(BOOST_NO_CXX11_NULLPTR) && !BOOST_WORKAROUND(BOOST_GCC, < 40800)
// Implementation based on the standard's rules of explicit type conversions.
// A pointer to an object of *derived* class type may be explicitly converted to a pointer to an *unambiguous* *base* class type.
// A pointer to an object of an *unambiguous* *non-virtual* *base* class type may be explicitly converted to a pointer of a *derived* class type.
// Therefore Derived has a virtual base Base if and only if
// (1) a Derived* can be converted to Base* (so the base class is unambiguous, which comes necessarily from virtual inheritance)
// (2) a Base* cannot be converted to Derived* (so the base class is either ambiguous or virtual)
// With both conditions true, Base must be a virtual base of Derived.
// The "is_base_of" is only needed so the compiler can (but is not required to) error out if the types are incomplete.
// This is in league with the the expected behaviour.
template<class T, class U>
constexpr bool is_virtual_base_impl(...) { return true; }
// C-style casts have the power to ignore inheritance visibility while still act as a static_cast.
// They can also fall back to the behaviour of reinterpret_cast, which allows is_virtual_base_of to work on non-class types too.
// Note that because we are casting pointers there can be no user-defined operators to interfere.
template<class T, class U,
boost::void_t<decltype((U*)(std::declval<T*>()))>* =
nullptr>
constexpr bool is_virtual_base_impl(int) { return false; }
} // namespace detail
template<class T, class U>
struct is_virtual_base_of : public
boost::integral_constant<
bool,
boost::is_base_of<T, U>::value &&
detail::is_virtual_base_impl<T, U>(0) &&
!detail::is_virtual_base_impl<U, T>(0)
> {};
#else
template<typename Base, typename Derived, typename tag>
struct is_virtual_base_of_impl
{
BOOST_STATIC_CONSTANT(bool, value = false);
};
template<typename Base, typename Derived>
struct is_virtual_base_of_impl<Base, Derived, true_type>
{
union max_align
{
unsigned u;
unsigned long ul;
void* v;
double d;
long double ld;
#ifndef BOOST_NO_LONG_LONG
long long ll;
#endif
};
#ifdef __BORLANDC__
struct boost_type_traits_internal_struct_X : public virtual Derived, public virtual Base
{
boost_type_traits_internal_struct_X();
boost_type_traits_internal_struct_X(const boost_type_traits_internal_struct_X&);
boost_type_traits_internal_struct_X& operator=(const boost_type_traits_internal_struct_X&);
~boost_type_traits_internal_struct_X()throw();
max_align data[4];
};
struct boost_type_traits_internal_struct_Y : public virtual Derived
{
boost_type_traits_internal_struct_Y();
boost_type_traits_internal_struct_Y(const boost_type_traits_internal_struct_Y&);
boost_type_traits_internal_struct_Y& operator=(const boost_type_traits_internal_struct_Y&);
~boost_type_traits_internal_struct_Y()throw();
max_align data[4];
};
#else
struct boost_type_traits_internal_struct_X : public Derived, virtual Base
{
boost_type_traits_internal_struct_X();
boost_type_traits_internal_struct_X(const boost_type_traits_internal_struct_X&);
boost_type_traits_internal_struct_X& operator=(const boost_type_traits_internal_struct_X&);
~boost_type_traits_internal_struct_X()throw();
max_align data[16];
};
struct boost_type_traits_internal_struct_Y : public Derived
{
boost_type_traits_internal_struct_Y();
boost_type_traits_internal_struct_Y(const boost_type_traits_internal_struct_Y&);
boost_type_traits_internal_struct_Y& operator=(const boost_type_traits_internal_struct_Y&);
~boost_type_traits_internal_struct_Y()throw();
max_align data[16];
};
#endif
BOOST_STATIC_CONSTANT(bool, value = (sizeof(boost_type_traits_internal_struct_X) == sizeof(boost_type_traits_internal_struct_Y)));
};
template<typename Base, typename Derived>
struct is_virtual_base_of_impl2
{
typedef boost::integral_constant<bool, (boost::is_base_of<Base, Derived>::value && !boost::is_same<Base, Derived>::value)> tag_type;
typedef is_virtual_base_of_impl<Base, Derived, tag_type> imp;
BOOST_STATIC_CONSTANT(bool, value = imp::value);
};
} // namespace detail
template <class Base, class Derived> struct is_virtual_base_of : public integral_constant<bool, (::boost::detail::is_virtual_base_of_impl2<Base, Derived>::value)> {};
#endif
template <class Base, class Derived> struct is_virtual_base_of<Base&, Derived> : public false_type{};
template <class Base, class Derived> struct is_virtual_base_of<Base, Derived&> : public false_type{};
template <class Base, class Derived> struct is_virtual_base_of<Base&, Derived&> : public false_type{};
#ifdef BOOST_MSVC
#pragma warning( pop )
#endif
} // namespace boost
#endif
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