Jeff Thompson | a28eed8 | 2013-08-22 16:21:10 -0700 | [diff] [blame] | 1 | |
| 2 | // (C) Copyright Rani Sharoni 2003. |
| 3 | // Use, modification and distribution are subject to the Boost Software License, |
| 4 | // Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at |
| 5 | // http://www.boost.org/LICENSE_1_0.txt). |
| 6 | // |
| 7 | // See http://www.boost.org/libs/type_traits for most recent version including documentation. |
| 8 | |
| 9 | #ifndef BOOST_TT_IS_BASE_AND_DERIVED_HPP_INCLUDED |
| 10 | #define BOOST_TT_IS_BASE_AND_DERIVED_HPP_INCLUDED |
| 11 | |
| 12 | #include <ndnboost/type_traits/intrinsics.hpp> |
| 13 | #ifndef BOOST_IS_BASE_OF |
| 14 | #include <ndnboost/type_traits/is_class.hpp> |
| 15 | #include <ndnboost/type_traits/is_same.hpp> |
| 16 | #include <ndnboost/type_traits/is_convertible.hpp> |
| 17 | #include <ndnboost/type_traits/detail/ice_and.hpp> |
| 18 | #include <ndnboost/config.hpp> |
| 19 | #include <ndnboost/static_assert.hpp> |
| 20 | #endif |
| 21 | #include <ndnboost/type_traits/remove_cv.hpp> |
| 22 | |
| 23 | // should be the last #include |
| 24 | #include <ndnboost/type_traits/detail/bool_trait_def.hpp> |
| 25 | |
| 26 | namespace ndnboost { |
| 27 | |
| 28 | namespace detail { |
| 29 | |
| 30 | #ifndef BOOST_IS_BASE_OF |
| 31 | #if !BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x581)) \ |
| 32 | && !BOOST_WORKAROUND(__SUNPRO_CC , <= 0x540) \ |
| 33 | && !BOOST_WORKAROUND(__EDG_VERSION__, <= 243) \ |
| 34 | && !BOOST_WORKAROUND(__DMC__, BOOST_TESTED_AT(0x840)) |
| 35 | |
| 36 | // The EDG version number is a lower estimate. |
| 37 | // It is not currently known which EDG version |
| 38 | // exactly fixes the problem. |
| 39 | |
| 40 | /************************************************************************* |
| 41 | |
| 42 | This version detects ambiguous base classes and private base classes |
| 43 | correctly, and was devised by Rani Sharoni. |
| 44 | |
| 45 | Explanation by Terje Slettebo and Rani Sharoni. |
| 46 | |
| 47 | Let's take the multiple base class below as an example, and the following |
| 48 | will also show why there's not a problem with private or ambiguous base |
| 49 | class: |
| 50 | |
| 51 | struct B {}; |
| 52 | struct B1 : B {}; |
| 53 | struct B2 : B {}; |
| 54 | struct D : private B1, private B2 {}; |
| 55 | |
| 56 | is_base_and_derived<B, D>::value; |
| 57 | |
| 58 | First, some terminology: |
| 59 | |
| 60 | SC - Standard conversion |
| 61 | UDC - User-defined conversion |
| 62 | |
| 63 | A user-defined conversion sequence consists of an SC, followed by an UDC, |
| 64 | followed by another SC. Either SC may be the identity conversion. |
| 65 | |
| 66 | When passing the default-constructed Host object to the overloaded check_sig() |
| 67 | functions (initialization 8.5/14/4/3), we have several viable implicit |
| 68 | conversion sequences: |
| 69 | |
| 70 | For "static no_type check_sig(B const volatile *, int)" we have the conversion |
| 71 | sequences: |
| 72 | |
| 73 | C -> C const (SC - Qualification Adjustment) -> B const volatile* (UDC) |
| 74 | C -> D const volatile* (UDC) -> B1 const volatile* / B2 const volatile* -> |
| 75 | B const volatile* (SC - Conversion) |
| 76 | |
| 77 | For "static yes_type check_sig(D const volatile *, T)" we have the conversion |
| 78 | sequence: |
| 79 | |
| 80 | C -> D const volatile* (UDC) |
| 81 | |
| 82 | According to 13.3.3.1/4, in context of user-defined conversion only the |
| 83 | standard conversion sequence is considered when selecting the best viable |
| 84 | function, so it only considers up to the user-defined conversion. For the |
| 85 | first function this means choosing between C -> C const and C -> C, and it |
| 86 | chooses the latter, because it's a proper subset (13.3.3.2/3/2) of the |
| 87 | former. Therefore, we have: |
| 88 | |
| 89 | C -> D const volatile* (UDC) -> B1 const volatile* / B2 const volatile* -> |
| 90 | B const volatile* (SC - Conversion) |
| 91 | C -> D const volatile* (UDC) |
| 92 | |
| 93 | Here, the principle of the "shortest subsequence" applies again, and it |
| 94 | chooses C -> D const volatile*. This shows that it doesn't even need to |
| 95 | consider the multiple paths to B, or accessibility, as that possibility is |
| 96 | eliminated before it could possibly cause ambiguity or access violation. |
| 97 | |
| 98 | If D is not derived from B, it has to choose between C -> C const -> B const |
| 99 | volatile* for the first function, and C -> D const volatile* for the second |
| 100 | function, which are just as good (both requires a UDC, 13.3.3.2), had it not |
| 101 | been for the fact that "static no_type check_sig(B const volatile *, int)" is |
| 102 | not templated, which makes C -> C const -> B const volatile* the best choice |
| 103 | (13.3.3/1/4), resulting in "no". |
| 104 | |
| 105 | Also, if Host::operator B const volatile* hadn't been const, the two |
| 106 | conversion sequences for "static no_type check_sig(B const volatile *, int)", in |
| 107 | the case where D is derived from B, would have been ambiguous. |
| 108 | |
| 109 | See also |
| 110 | http://groups.google.com/groups?selm=df893da6.0301280859.522081f7%40posting. |
| 111 | google.com and links therein. |
| 112 | |
| 113 | *************************************************************************/ |
| 114 | |
| 115 | template <typename B, typename D> |
| 116 | struct bd_helper |
| 117 | { |
| 118 | // |
| 119 | // This VC7.1 specific workaround stops the compiler from generating |
| 120 | // an internal compiler error when compiling with /vmg (thanks to |
| 121 | // Aleksey Gurtovoy for figuring out the workaround). |
| 122 | // |
| 123 | #if !BOOST_WORKAROUND(BOOST_MSVC, == 1310) |
| 124 | template <typename T> |
| 125 | static type_traits::yes_type check_sig(D const volatile *, T); |
| 126 | static type_traits::no_type check_sig(B const volatile *, int); |
| 127 | #else |
| 128 | static type_traits::yes_type check_sig(D const volatile *, long); |
| 129 | static type_traits::no_type check_sig(B const volatile * const&, int); |
| 130 | #endif |
| 131 | }; |
| 132 | |
| 133 | template<typename B, typename D> |
| 134 | struct is_base_and_derived_impl2 |
| 135 | { |
| 136 | #if BOOST_WORKAROUND(BOOST_MSVC_FULL_VER, >= 140050000) |
| 137 | #pragma warning(push) |
| 138 | #pragma warning(disable:6334) |
| 139 | #endif |
| 140 | // |
| 141 | // May silently do the wrong thing with incomplete types |
| 142 | // unless we trap them here: |
| 143 | // |
| 144 | BOOST_STATIC_ASSERT(sizeof(B) != 0); |
| 145 | BOOST_STATIC_ASSERT(sizeof(D) != 0); |
| 146 | |
| 147 | struct Host |
| 148 | { |
| 149 | #if !BOOST_WORKAROUND(BOOST_MSVC, == 1310) |
| 150 | operator B const volatile *() const; |
| 151 | #else |
| 152 | operator B const volatile * const&() const; |
| 153 | #endif |
| 154 | operator D const volatile *(); |
| 155 | }; |
| 156 | |
| 157 | BOOST_STATIC_CONSTANT(bool, value = |
| 158 | sizeof(bd_helper<B,D>::check_sig(Host(), 0)) == sizeof(type_traits::yes_type)); |
| 159 | #if BOOST_WORKAROUND(BOOST_MSVC_FULL_VER, >= 140050000) |
| 160 | #pragma warning(pop) |
| 161 | #endif |
| 162 | }; |
| 163 | |
| 164 | #else |
| 165 | |
| 166 | // |
| 167 | // broken version: |
| 168 | // |
| 169 | template<typename B, typename D> |
| 170 | struct is_base_and_derived_impl2 |
| 171 | { |
| 172 | BOOST_STATIC_CONSTANT(bool, value = |
| 173 | (::ndnboost::is_convertible<D*,B*>::value)); |
| 174 | }; |
| 175 | |
| 176 | #define BOOST_BROKEN_IS_BASE_AND_DERIVED |
| 177 | |
| 178 | #endif |
| 179 | |
| 180 | template <typename B, typename D> |
| 181 | struct is_base_and_derived_impl3 |
| 182 | { |
| 183 | BOOST_STATIC_CONSTANT(bool, value = false); |
| 184 | }; |
| 185 | |
| 186 | template <bool ic1, bool ic2, bool iss> |
| 187 | struct is_base_and_derived_select |
| 188 | { |
| 189 | template <class T, class U> |
| 190 | struct rebind |
| 191 | { |
| 192 | typedef is_base_and_derived_impl3<T,U> type; |
| 193 | }; |
| 194 | }; |
| 195 | |
| 196 | template <> |
| 197 | struct is_base_and_derived_select<true,true,false> |
| 198 | { |
| 199 | template <class T, class U> |
| 200 | struct rebind |
| 201 | { |
| 202 | typedef is_base_and_derived_impl2<T,U> type; |
| 203 | }; |
| 204 | }; |
| 205 | |
| 206 | template <typename B, typename D> |
| 207 | struct is_base_and_derived_impl |
| 208 | { |
| 209 | typedef typename remove_cv<B>::type ncvB; |
| 210 | typedef typename remove_cv<D>::type ncvD; |
| 211 | |
| 212 | typedef is_base_and_derived_select< |
| 213 | ::ndnboost::is_class<B>::value, |
| 214 | ::ndnboost::is_class<D>::value, |
| 215 | ::ndnboost::is_same<ncvB,ncvD>::value> selector; |
| 216 | typedef typename selector::template rebind<ncvB,ncvD> binder; |
| 217 | typedef typename binder::type bound_type; |
| 218 | |
| 219 | BOOST_STATIC_CONSTANT(bool, value = bound_type::value); |
| 220 | }; |
| 221 | #else |
| 222 | template <typename B, typename D> |
| 223 | struct is_base_and_derived_impl |
| 224 | { |
| 225 | typedef typename remove_cv<B>::type ncvB; |
| 226 | typedef typename remove_cv<D>::type ncvD; |
| 227 | |
| 228 | BOOST_STATIC_CONSTANT(bool, value = (BOOST_IS_BASE_OF(B,D) && ! ::ndnboost::is_same<ncvB,ncvD>::value)); |
| 229 | }; |
| 230 | #endif |
| 231 | } // namespace detail |
| 232 | |
| 233 | BOOST_TT_AUX_BOOL_TRAIT_DEF2( |
| 234 | is_base_and_derived |
| 235 | , Base |
| 236 | , Derived |
| 237 | , (::ndnboost::detail::is_base_and_derived_impl<Base,Derived>::value) |
| 238 | ) |
| 239 | |
| 240 | #ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION |
| 241 | BOOST_TT_AUX_BOOL_TRAIT_PARTIAL_SPEC2_2(typename Base,typename Derived,is_base_and_derived,Base&,Derived,false) |
| 242 | BOOST_TT_AUX_BOOL_TRAIT_PARTIAL_SPEC2_2(typename Base,typename Derived,is_base_and_derived,Base,Derived&,false) |
| 243 | BOOST_TT_AUX_BOOL_TRAIT_PARTIAL_SPEC2_2(typename Base,typename Derived,is_base_and_derived,Base&,Derived&,false) |
| 244 | #endif |
| 245 | |
| 246 | #if BOOST_WORKAROUND(__CODEGEARC__, BOOST_TESTED_AT(0x610)) |
| 247 | BOOST_TT_AUX_BOOL_TRAIT_PARTIAL_SPEC2_1(typename Base,is_base_and_derived,Base,Base,false) |
| 248 | #endif |
| 249 | |
| 250 | } // namespace ndnboost |
| 251 | |
| 252 | #include <ndnboost/type_traits/detail/bool_trait_undef.hpp> |
| 253 | |
| 254 | #endif // BOOST_TT_IS_BASE_AND_DERIVED_HPP_INCLUDED |