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