boost/boost/mpl/has_xxx.hpp

   1
   2 #ifndef BOOST_MPL_HAS_XXX_HPP_INCLUDED
   3 #define BOOST_MPL_HAS_XXX_HPP_INCLUDED
   4
   5 // Copyright Aleksey Gurtovoy 2002-2004
   6 // Copyright David Abrahams 2002-2003
   7 //
   8 // Distributed under the Boost Software License, Version 1.0.
   9 // (See accompanying file LICENSE_1_0.txt or copy at
  10 // http://www.boost.org/LICENSE_1_0.txt)
  11 //
  12 // See http://www.boost.org/libs/mpl for documentation.
  13
  14 // $Source: /cvsroot/boost/boost/boost/mpl/has_xxx.hpp,v $
  15 // $Date: 2005/06/15 10:43:23 $
  16 // $Revision: 1.4 $
  17
  18 #include <boost/mpl/bool.hpp>
  19 #include <boost/mpl/aux_/type_wrapper.hpp>
  20 #include <boost/mpl/aux_/yes_no.hpp>
  21 #include <boost/mpl/aux_/config/has_xxx.hpp>
  22 #include <boost/mpl/aux_/config/msvc_typename.hpp>
  23 #include <boost/mpl/aux_/config/msvc.hpp>
  24 #include <boost/mpl/aux_/config/static_constant.hpp>
  25 #include <boost/mpl/aux_/config/workaround.hpp>
  26
  27 #include <boost/preprocessor/cat.hpp>
  28
  29 #if !defined(BOOST_MPL_CFG_NO_HAS_XXX)
  30
  31 #   if BOOST_WORKAROUND(BOOST_MSVC, <= 1300)
  32
  33 // agurt, 11/sep/02: MSVC-specific version (< 7.1), based on a USENET
  34 // newsgroup's posting by John Madsen (comp.lang.c++.moderated,
  35 // 1999-11-12 19:17:06 GMT); the code is _not_ standard-conforming, but
  36 // it works way more reliably than the SFINAE-based implementation
  37
  38 // Modified dwa 8/Oct/02 to handle reference types.
  39
  40 #   include <boost/mpl/if.hpp>
  41 #   include <boost/mpl/bool.hpp>
  42
  43 namespace boost { namespace mpl { namespace aux {
  44
  45 struct has_xxx_tag;
  46
  47 #if BOOST_WORKAROUND(BOOST_MSVC, == 1300)
  48 template< typename U > struct msvc_incomplete_array
  49 {
  50     typedef char (&type)[sizeof(U) + 1];
  51 };
  52 #endif
  53
  54 template< typename T >
  55 struct msvc_is_incomplete
  56 {
  57     // MSVC is capable of some kinds of SFINAE.  If U is an incomplete
  58     // type, it won't pick the second overload
  59     static char tester(...);
  60
  61 #if BOOST_WORKAROUND(BOOST_MSVC, == 1300)
  62     template< typename U >
  63     static typename msvc_incomplete_array<U>::type tester(type_wrapper<U>);
  64 #else
  65     template< typename U >
  66     static char (& tester(type_wrapper<U>) )[sizeof(U)+1];
  67 #endif
  68
  69     BOOST_STATIC_CONSTANT(bool, value =
  70           sizeof(tester(type_wrapper<T>())) == 1
  71         );
  72 };
  73
  74 template<>
  75 struct msvc_is_incomplete<int>
  76 {
  77     BOOST_STATIC_CONSTANT(bool, value = false);
  78 };
  79
  80 }}}
  81
  82 #   define BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF_(trait, name, default_) \
  83 template< typename T, typename name = ::boost::mpl::aux::has_xxx_tag > \
  84 struct BOOST_PP_CAT(trait,_impl) : T \
  85 { \
  86     static boost::mpl::aux::no_tag \
  87     test(void(*)(::boost::mpl::aux::has_xxx_tag)); \
  88     \
  89     static boost::mpl::aux::yes_tag test(...); \
  90     \
  91     BOOST_STATIC_CONSTANT(bool, value = \
  92           sizeof(test(static_cast<void(*)(name)>(0))) \
  93             != sizeof(boost::mpl::aux::no_tag) \
  94         ); \
  95     typedef boost::mpl::bool_<value> type; \
  96 }; \
  97 \
  98 template< typename T, typename fallback_ = boost::mpl::bool_<default_> > \
  99 struct trait \
 100     : boost::mpl::if_c< \
 101           boost::mpl::aux::msvc_is_incomplete<T>::value \
 102         , boost::mpl::bool_<false> \
 103         , BOOST_PP_CAT(trait,_impl)<T> \
 104         >::type \
 105 { \
 106 }; \
 107 \
 108 BOOST_MPL_AUX_HAS_XXX_TRAIT_SPEC(trait, void) \
 109 BOOST_MPL_AUX_HAS_XXX_TRAIT_SPEC(trait, bool) \
 110 BOOST_MPL_AUX_HAS_XXX_TRAIT_SPEC(trait, char) \
 111 BOOST_MPL_AUX_HAS_XXX_TRAIT_SPEC(trait, signed char) \
 112 BOOST_MPL_AUX_HAS_XXX_TRAIT_SPEC(trait, unsigned char) \
 113 BOOST_MPL_AUX_HAS_XXX_TRAIT_SPEC(trait, signed short) \
 114 BOOST_MPL_AUX_HAS_XXX_TRAIT_SPEC(trait, unsigned short) \
 115 BOOST_MPL_AUX_HAS_XXX_TRAIT_SPEC(trait, signed int) \
 116 BOOST_MPL_AUX_HAS_XXX_TRAIT_SPEC(trait, unsigned int) \
 117 BOOST_MPL_AUX_HAS_XXX_TRAIT_SPEC(trait, signed long) \
 118 BOOST_MPL_AUX_HAS_XXX_TRAIT_SPEC(trait, unsigned long) \
 119 BOOST_MPL_AUX_HAS_XXX_TRAIT_SPEC(trait, float) \
 120 BOOST_MPL_AUX_HAS_XXX_TRAIT_SPEC(trait, double) \
 121 BOOST_MPL_AUX_HAS_XXX_TRAIT_SPEC(trait, long double) \
 122 /**/
 123
 124 #   define BOOST_MPL_AUX_HAS_XXX_TRAIT_SPEC(trait, T) \
 125 template<> struct trait<T> \
 126 { \
 127     BOOST_STATIC_CONSTANT(bool, value = false); \
 128     typedef boost::mpl::bool_<false> type; \
 129 }; \
 130 /**/
 131
 132 #if !defined(BOOST_NO_INTRINSIC_WCHAR_T)
 133 #   define BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF(trait, name, unused) \
 134     BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF_(trait, name, unused) \
 135     BOOST_MPL_AUX_HAS_XXX_TRAIT_SPEC(trait, wchar_t) \
 136 /**/
 137 #else
 138 #   define BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF(trait, name, unused) \
 139     BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF_(trait, name, unused) \
 140 /**/
 141 #endif
 142
 143
 144 // SFINAE-based implementations below are derived from a USENET newsgroup's
 145 // posting by Rani Sharoni (comp.lang.c++.moderated, 2002-03-17 07:45:09 PST)
 146
 147 #   elif BOOST_WORKAROUND(BOOST_MSVC, BOOST_TESTED_AT(1400))
 148
 149 // MSVC 7.1+
 150
 151 // agurt, 15/jun/05: replace overload-based SFINAE implementation with SFINAE
 152 // applied to partial specialization to fix some apparently random failures
 153 // (thanks to Daniel Wallin for researching this!)
 154
 155 namespace boost { namespace mpl { namespace aux {
 156 template< typename T > struct msvc71_sfinae_helper { typedef void type; };
 157 }}}
 158
 159 #   define BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF(trait, name, default_) \
 160 template< typename T, typename U = void > \
 161 struct BOOST_PP_CAT(trait,_impl_) \
 162 { \
 163     BOOST_STATIC_CONSTANT(bool, value = false); \
 164     typedef boost::mpl::bool_<value> type; \
 165 }; \
 166 \
 167 template< typename T > \
 168 struct BOOST_PP_CAT(trait,_impl_)< \
 169       T \
 170     , typename boost::mpl::aux::msvc71_sfinae_helper< typename T::name >::type \
 171     > \
 172 { \
 173     BOOST_STATIC_CONSTANT(bool, value = true); \
 174     typedef boost::mpl::bool_<value> type; \
 175 }; \
 176 \
 177 template< typename T, typename fallback_ = boost::mpl::bool_<default_> > \
 178 struct trait \
 179     : BOOST_PP_CAT(trait,_impl_)<T> \
 180 { \
 181 }; \
 182 /**/
 183
 184 #   else // other SFINAE-capable compilers
 185
 186 #   define BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF(trait, name, default_) \
 187 template< typename T, typename fallback_ = boost::mpl::bool_<default_> > \
 188 struct trait \
 189 { \
 190     struct gcc_3_2_wknd \
 191     { \
 192         template< typename U > \
 193         static boost::mpl::aux::yes_tag test( \
 194               boost::mpl::aux::type_wrapper<U> const volatile* \
 195             , boost::mpl::aux::type_wrapper<BOOST_MSVC_TYPENAME U::name>* = 0 \
 196             ); \
 197     \
 198         static boost::mpl::aux::no_tag test(...); \
 199     }; \
 200     \
 201     typedef boost::mpl::aux::type_wrapper<T> t_; \
 202     BOOST_STATIC_CONSTANT(bool, value = \
 203           sizeof(gcc_3_2_wknd::test(static_cast<t_*>(0))) \
 204             == sizeof(boost::mpl::aux::yes_tag) \
 205         ); \
 206     typedef boost::mpl::bool_<value> type; \
 207 }; \
 208 /**/
 209
 210 #   endif // BOOST_WORKAROUND(BOOST_MSVC, <= 1300)
 211
 212
 213 #else // BOOST_MPL_CFG_NO_HAS_XXX
 214
 215 // placeholder implementation
 216
 217 #   define BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF(trait, name, default_) \
 218 template< typename T, typename fallback_ = boost::mpl::bool_<default_> > \
 219 struct trait \
 220 { \
 221     BOOST_STATIC_CONSTANT(bool, value = fallback_::value); \
 222     typedef fallback_ type; \
 223 }; \
 224 /**/
 225
 226 #endif
 227
 228 #define BOOST_MPL_HAS_XXX_TRAIT_DEF(name) \
 229     BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF(BOOST_PP_CAT(has_,name), name, false) \
 230 /**/
 231
 232 #endif // BOOST_MPL_HAS_XXX_HPP_INCLUDED