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| author | Jonathan Wakely <jwakely@redhat.com> | 2016-10-14 17:12:21 +0100 |
|---|---|---|
| committer | Jonathan Wakely <redi@gcc.gnu.org> | 2016-10-14 17:12:21 +0100 |
| commit | a4744f620f32b6b859a39c6876f5e21b52b1af4b (patch) | |
| tree | 1066398a67a405a7006243379c47c61cdac0098d /libstdc++-v3/include/std | |
| parent | 30cd7c740ce5525181b557b51238963260f16637 (diff) | |
| download | gcc-a4744f620f32b6b859a39c6876f5e21b52b1af4b.zip gcc-a4744f620f32b6b859a39c6876f5e21b52b1af4b.tar.gz gcc-a4744f620f32b6b859a39c6876f5e21b52b1af4b.tar.bz2 | |
Avoid copies in std::scoped_allocator_adaptor piecewise construction
* include/std/scoped_allocator (scoped_allocator_adaptor): Forward
piecewise construction arguments as tuples of references, to avoid
copies (related to LWG 2511).
* testsuite/20_util/scoped_allocator/construct_pair.cc: New test.
From-SVN: r241169
Diffstat (limited to 'libstdc++-v3/include/std')
| -rw-r--r-- | libstdc++-v3/include/std/scoped_allocator | 35 |
1 files changed, 19 insertions, 16 deletions
diff --git a/libstdc++-v3/include/std/scoped_allocator b/libstdc++-v3/include/std/scoped_allocator index 39762fe..dcb97df 100644 --- a/libstdc++-v3/include/std/scoped_allocator +++ b/libstdc++-v3/include/std/scoped_allocator @@ -369,10 +369,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION = __use_alloc<_T1, inner_allocator_type, _Args1...>(__inner); auto __y_use_tag = __use_alloc<_T2, inner_allocator_type, _Args2...>(__inner); + typename _Build_index_tuple<sizeof...(_Args1)>::__type __x_indices; + typename _Build_index_tuple<sizeof...(_Args2)>::__type __y_indices; typedef __outermost_alloc_traits<scoped_allocator_adaptor> _O_traits; _O_traits::construct(__outermost(*this), __p, piecewise_construct, - _M_construct_p(__x_use_tag, __x), - _M_construct_p(__y_use_tag, __y)); + _M_construct_p(__x_use_tag, __x_indices, __x), + _M_construct_p(__y_use_tag, __y_indices, __y)); } template<typename _T1, typename _T2> @@ -428,26 +430,27 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION const scoped_allocator_adaptor<_OutA2, _InA...>& __b) noexcept; private: - template<typename _Tuple> - _Tuple&& - _M_construct_p(__uses_alloc0, _Tuple& __t) + template<typename _Ind, typename... _Args> + tuple<_Args&&...> + _M_construct_p(__uses_alloc0, _Ind, tuple<_Args...>& __t) { return std::move(__t); } - template<typename... _Args> - std::tuple<allocator_arg_t, inner_allocator_type&, _Args...> - _M_construct_p(__uses_alloc1_, std::tuple<_Args...>& __t) + template<size_t... _Ind, typename... _Args> + tuple<allocator_arg_t, inner_allocator_type&, _Args&&...> + _M_construct_p(__uses_alloc1_, _Index_tuple<_Ind...>, + tuple<_Args...>& __t) { - typedef std::tuple<allocator_arg_t, inner_allocator_type&> _Tuple; - return std::tuple_cat(_Tuple(allocator_arg, inner_allocator()), - std::move(__t)); + return { allocator_arg, inner_allocator(), + std::get<_Ind>(std::move(__t))... + }; } - template<typename... _Args> - std::tuple<_Args..., inner_allocator_type&> - _M_construct_p(__uses_alloc2_, std::tuple<_Args...>& __t) + template<size_t... _Ind, typename... _Args> + tuple<_Args&&..., inner_allocator_type&> + _M_construct_p(__uses_alloc2_, _Index_tuple<_Ind...>, + tuple<_Args...>& __t) { - typedef std::tuple<inner_allocator_type&> _Tuple; - return std::tuple_cat(std::move(__t), _Tuple(inner_allocator())); + return { std::get<_Ind>(std::move(__t))..., inner_allocator() }; } }; |