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Reuse is_swappable implementation in is_nothrow_swappable for gcc < 4.7.

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This avoids applying noexcept operator to a potentially invalid
swap expression, which should resolve ICE with gcc 4.6.
This commit is contained in:
Andrey Semashev
2023-02-18 19:58:36 +03:00
parent fc61f298bf
commit 5f43b22861
4 changed files with 21 additions and 5 deletions
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1
doc/history.qbk
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@ -10,6 +10,7 @@
[h4 Boost-1.82.0]
* Added __is_swappable trait.
* Added a workaround for gcc 4.6 that allows __is_nothrow_swappable to work.
[h4 Boost-1.70.0]

21
include/boost/type_traits/detail/is_swappable_cxx_11.hpp
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@ -34,7 +34,22 @@ template<class T> boost::false_type is_swappable_impl( ... );
template<class T>
struct is_swappable_helper { typedef decltype( boost_type_traits_swappable_detail::is_swappable_impl<T>(0) ) type; };
#if !defined(BOOST_NO_CXX11_NOEXCEPT) && !BOOST_WORKAROUND(BOOST_GCC, < 40700)
#if !defined(BOOST_NO_CXX11_NOEXCEPT)
#if BOOST_WORKAROUND(BOOST_GCC, < 40700)
// gcc 4.6 ICEs when noexcept operator is used on an invalid expression
template<class T, class U, bool = is_swappable_with_helper<T, U>::type::value>
struct is_nothrow_swappable_with_helper { typedef boost::false_type type; };
template<class T, class U>
struct is_nothrow_swappable_with_helper<T, U, true> { typedef boost::integral_constant<bool, noexcept(swap(boost::declval<T>(), boost::declval<U>()))> type; };
template<class T, bool = is_swappable_helper<T>::type::value>
struct is_nothrow_swappable_helper { typedef boost::false_type type; };
template<class T>
struct is_nothrow_swappable_helper<T, true> { typedef boost::integral_constant<bool, noexcept(swap(boost::declval<T&>(), boost::declval<T&>()))> type; };
#else // BOOST_WORKAROUND(BOOST_GCC, < 40700)
template<class T, class U, bool B = noexcept(swap(boost::declval<T>(), boost::declval<U>()))> boost::integral_constant<bool, B> is_nothrow_swappable_with_impl( int );
template<class T, class U> boost::false_type is_nothrow_swappable_with_impl( ... );
@ -46,7 +61,9 @@ template<class T> boost::false_type is_nothrow_swappable_impl( ... );
template<class T>
struct is_nothrow_swappable_helper { typedef decltype( boost_type_traits_swappable_detail::is_nothrow_swappable_impl<T>(0) ) type; };
#endif // !defined(BOOST_NO_CXX11_NOEXCEPT) && !BOOST_WORKAROUND(BOOST_GCC, < 40700)
#endif // BOOST_WORKAROUND(BOOST_GCC, < 40700)
#endif // !defined(BOOST_NO_CXX11_NOEXCEPT)
} // namespace boost_type_traits_swappable_detail

3
include/boost/type_traits/is_nothrow_swappable.hpp
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@ -8,10 +8,9 @@
// http://www.boost.org/LICENSE_1_0.txt
#include <boost/config.hpp>
#include <boost/config/workaround.hpp>
#if defined(BOOST_NO_SFINAE_EXPR) || defined(BOOST_NO_CXX11_NOEXCEPT) || defined(BOOST_NO_CXX11_DECLTYPE) \
|| defined(BOOST_NO_CXX11_FUNCTION_TEMPLATE_DEFAULT_ARGS) || BOOST_WORKAROUND(BOOST_GCC, < 40700)
|| defined(BOOST_NO_CXX11_FUNCTION_TEMPLATE_DEFAULT_ARGS)
#include <boost/type_traits/is_scalar.hpp>
#include <boost/type_traits/is_const.hpp>

1
test/is_nothrow_swappable_test.cpp
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@ -18,7 +18,6 @@
// These conditions should be similar to those in is_nothrow_swappable.hpp
#if defined(BOOST_NO_SFINAE_EXPR) || defined(BOOST_NO_CXX11_NOEXCEPT) || defined(BOOST_NO_CXX11_DECLTYPE) || defined(BOOST_NO_CXX11_FUNCTION_TEMPLATE_DEFAULT_ARGS) \
|| BOOST_WORKAROUND(BOOST_GCC, < 40700) \
|| (defined(__GLIBCXX__) && __GLIBCXX__ <= 20120301) // built-in clang++ -std=c++11 on Travis, w/ libstdc++ 4.6
#define BOOST_TYPE_TRAITS_IS_NOTHROW_SWAPPABLE_EMULATED
#endif