boost/type_traits/is_empty.hpp
// (C) Copyright Steve Cleary, Beman Dawes, Howard Hinnant & John Maddock 2000. // 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_EMPTY_HPP_INCLUDED #define BOOST_TT_IS_EMPTY_HPP_INCLUDED #include <boost/type_traits/is_convertible.hpp> #include <boost/type_traits/detail/ice_or.hpp> #include <boost/type_traits/config.hpp> #include <boost/type_traits/intrinsics.hpp> #ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION # include <boost/type_traits/remove_cv.hpp> # include <boost/type_traits/is_class.hpp> # include <boost/type_traits/add_reference.hpp> #else # include <boost/type_traits/is_reference.hpp> # include <boost/type_traits/is_pointer.hpp> # include <boost/type_traits/is_member_pointer.hpp> # include <boost/type_traits/is_array.hpp> # include <boost/type_traits/is_void.hpp> # include <boost/type_traits/detail/ice_and.hpp> # include <boost/type_traits/detail/ice_not.hpp> #endif // should be always the last #include directive #include <boost/type_traits/detail/bool_trait_def.hpp> #ifndef BOOST_INTERNAL_IS_EMPTY #define BOOST_INTERNAL_IS_EMPTY(T) false #else #define BOOST_INTERNAL_IS_EMPTY(T) BOOST_IS_EMPTY(T) #endif namespace boost { namespace detail { #ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION #ifdef BOOST_MSVC #pragma warning(push) #pragma warning(disable:4624) // destructor could not be generated #endif template <typename T> struct empty_helper_t1 : public T { empty_helper_t1(); // hh compiler bug workaround int i[256]; private: // suppress compiler warnings: empty_helper_t1(const empty_helper_t1&); empty_helper_t1& operator=(const empty_helper_t1&); }; #ifdef BOOST_MSVC #pragma warning(pop) #endif struct empty_helper_t2 { int i[256]; }; #if !BOOST_WORKAROUND(__BORLANDC__, < 0x600) template <typename T, bool is_a_class = false> struct empty_helper { BOOST_STATIC_CONSTANT(bool, value = false); }; template <typename T> struct empty_helper<T, true> { BOOST_STATIC_CONSTANT( bool, value = (sizeof(empty_helper_t1<T>) == sizeof(empty_helper_t2)) ); }; template <typename T> struct is_empty_impl { typedef typename remove_cv<T>::type cvt; BOOST_STATIC_CONSTANT( bool, value = ( ::boost::type_traits::ice_or< ::boost::detail::empty_helper<cvt,::boost::is_class<T>::value>::value , BOOST_INTERNAL_IS_EMPTY(cvt) >::value )); }; #else // __BORLANDC__ template <typename T, bool is_a_class, bool convertible_to_int> struct empty_helper { BOOST_STATIC_CONSTANT(bool, value = false); }; template <typename T> struct empty_helper<T, true, false> { BOOST_STATIC_CONSTANT(bool, value = ( sizeof(empty_helper_t1<T>) == sizeof(empty_helper_t2) )); }; template <typename T> struct is_empty_impl { typedef typename remove_cv<T>::type cvt; typedef typename add_reference<T>::type r_type; BOOST_STATIC_CONSTANT( bool, value = ( ::boost::type_traits::ice_or< ::boost::detail::empty_helper< cvt , ::boost::is_class<T>::value , ::boost::is_convertible< r_type,int>::value >::value , BOOST_INTERNAL_IS_EMPTY(cvt) >::value)); }; #endif // __BORLANDC__ #else // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION #ifdef BOOST_MSVC6_MEMBER_TEMPLATES template <typename T> struct empty_helper_t1 : public T { empty_helper_t1(); int i[256]; }; struct empty_helper_t2 { int i[256]; }; template <typename T> struct empty_helper_base { enum { value = (sizeof(empty_helper_t1<T>) == sizeof(empty_helper_t2)) }; }; template <typename T> struct empty_helper_nonbase { enum { value = false }; }; template <bool base> struct empty_helper_chooser { template <typename T> struct result_ { typedef empty_helper_nonbase<T> type; }; }; template <> struct empty_helper_chooser<true> { template <typename T> struct result_ { typedef empty_helper_base<T> type; }; }; template <typename T> struct is_empty_impl { typedef ::boost::detail::empty_helper_chooser< ::boost::type_traits::ice_and< ::boost::type_traits::ice_not< ::boost::is_reference<T>::value >::value, ::boost::type_traits::ice_not< ::boost::is_convertible<T,double>::value >::value, ::boost::type_traits::ice_not< ::boost::is_pointer<T>::value >::value, ::boost::type_traits::ice_not< ::boost::is_member_pointer<T>::value >::value, ::boost::type_traits::ice_not< ::boost::is_array<T>::value >::value, ::boost::type_traits::ice_not< ::boost::is_void<T>::value >::value, ::boost::type_traits::ice_not< ::boost::is_convertible<T,void const volatile*>::value >::value >::value > chooser; typedef typename chooser::template result_<T> result; typedef typename result::type eh_type; BOOST_STATIC_CONSTANT(bool, value = (::boost::type_traits::ice_or<eh_type::value, BOOST_INTERNAL_IS_EMPTY(T)>::value)); }; #else template <typename T> struct is_empty_impl { BOOST_STATIC_CONSTANT(bool, value = BOOST_INTERNAL_IS_EMPTY(T)); }; #endif // BOOST_MSVC6_MEMBER_TEMPLATES #endif // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION // these help when the compiler has no partial specialization support: BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_empty,void,false) #ifndef BOOST_NO_CV_VOID_SPECIALIZATIONS BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_empty,void const,false) BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_empty,void volatile,false) BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_empty,void const volatile,false) #endif } // namespace detail BOOST_TT_AUX_BOOL_TRAIT_DEF1(is_empty,T,::boost::detail::is_empty_impl<T>::value) } // namespace boost #include <boost/type_traits/detail/bool_trait_undef.hpp> #undef BOOST_INTERNAL_IS_EMPTY #endif // BOOST_TT_IS_EMPTY_HPP_INCLUDED