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Use defaulted template arguments to restrict boost::ref converting ctor.

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This commit is contained in:
Andrey Semashev
2023-01-06 19:38:55 +03:00
parent 1825265014
commit 1e84baeea3
1 changed files with 13 additions and 6 deletions
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19
include/boost/core/ref.hpp
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@ -1,17 +1,15 @@
#ifndef BOOST_CORE_REF_HPP #ifndef BOOST_CORE_REF_HPP
#define BOOST_CORE_REF_HPP #define BOOST_CORE_REF_HPP
// MS compatible compilers support #pragma once
#if defined(_MSC_VER) && (_MSC_VER >= 1020)
# pragma once
#endif
#include <boost/config.hpp> #include <boost/config.hpp>
#include <boost/config/workaround.hpp> #include <boost/config/workaround.hpp>
#include <boost/core/addressof.hpp> #include <boost/core/addressof.hpp>
#include <boost/core/enable_if.hpp> #include <boost/core/enable_if.hpp>
#if defined(BOOST_HAS_PRAGMA_ONCE)
# pragma once
#endif
// //
// ref.hpp - ref/cref, useful helper functions // ref.hpp - ref/cref, useful helper functions
// //
@ -61,9 +59,11 @@ template< class Y, class T > struct ref_convertible
enum _vt { value = sizeof( (f)( static_cast<Y*>(0) ) ) == sizeof(yes) }; enum _vt { value = sizeof( (f)( static_cast<Y*>(0) ) ) == sizeof(yes) };
}; };
#if !defined(BOOST_NO_CXX11_FUNCTION_TEMPLATE_DEFAULT_ARGS)
struct ref_empty struct ref_empty
{ {
}; };
#endif
} // namespace detail } // namespace detail
@ -117,11 +117,18 @@ public:
@remark Only enabled when `Y*` is convertible to `T*`. @remark Only enabled when `Y*` is convertible to `T*`.
@remark Does not throw. @remark Does not throw.
*/ */
#if !defined(BOOST_NO_CXX11_FUNCTION_TEMPLATE_DEFAULT_ARGS)
template<class Y, class = typename enable_if_c<boost::detail::ref_convertible<Y, T>::value>::type>
reference_wrapper( reference_wrapper<Y> r ) BOOST_NOEXCEPT : t_( r.t_ )
{
}
#else
template<class Y> reference_wrapper( reference_wrapper<Y> r, template<class Y> reference_wrapper( reference_wrapper<Y> r,
typename enable_if_c<boost::detail::ref_convertible<Y, T>::value, typename enable_if_c<boost::detail::ref_convertible<Y, T>::value,
boost::detail::ref_empty>::type = boost::detail::ref_empty() ) BOOST_NOEXCEPT : t_( r.t_ ) boost::detail::ref_empty>::type = boost::detail::ref_empty() ) BOOST_NOEXCEPT : t_( r.t_ )
{ {
} }
#endif
/** /**
@return The stored reference. @return The stored reference.