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Reverted default implementation to old version,

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the new version doesn't quite work for all the cases required.


[SVN r16082]
This commit is contained in:
John Maddock
2002-11-03 12:35:22 +00:00
parent 026434c941
commit bac27107b7
1 changed files with 26 additions and 2 deletions
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28
include/boost/type_traits/is_convertible.hpp
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@ -125,8 +125,13 @@ struct is_convertible_impl
== sizeof(::boost::type_traits::yes_type);
};
#else
#elif 0
//
// This is *almost* an ideal world implementation as it doesn't rely
// on undefined behaviour by passing UDT's through (...).
// Unfortunately it doesn't quite pass all the tests for most compilers (sigh...)
// Enable this for your compiler if is_convertible_test.cpp will compile it...
//
struct any_conversion
{
template <typename T> any_conversion(const volatile T&);
@ -145,6 +150,24 @@ struct is_convertible_impl
);
};
#else
//
// This version seems to work pretty well for a wide spectrum of compilers,
// however it does rely on undefined behaviour by passing UDT's through (...).
//
template <typename From, typename To>
struct is_convertible_impl
{
static ::boost::type_traits::no_type BOOST_TT_DECL _m_check(...);
static ::boost::type_traits::yes_type BOOST_TT_DECL _m_check(To);
static From _m_from;
BOOST_STATIC_CONSTANT(bool, value =
sizeof( _m_check(_m_from) ) == sizeof(::boost::type_traits::yes_type)
);
};
#endif // is_convertible_impl
} // namespace detail
@ -240,3 +263,4 @@ TT_AUX_IS_CONVERTIBLE_FROM_FLOAT_CV_SPEC(long double)
#include "boost/type_traits/detail/bool_trait_undef.hpp"
#endif // BOOST_TT_IS_CONVERTIBLE_HPP_INCLUDED