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| author | Louis Dionne <ldionne.2@gmail.com> | 2025-05-08 16:35:00 -0400 |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2025-05-08 16:35:00 -0400 |
| commit | 45d493b680e3e79e4e9c19d665df83823c52a73a (patch) | |
| tree | 461ff7a2c9c3f7e4cd6ac5decfcee1f86bfc4632 /libcxx/include/tuple | |
| parent | c82e2f5c9ed08a270a1ec60bf7313af9c236ab98 (diff) | |
[libc++] Add the __is_replaceable type trait (#132408)
That type trait represents whether move-assigning an object is
equivalent to destroying it and then move-constructing a new one from
the same argument. This will be useful in a few places where we may want
to destroy + construct instead of doing an assignment, in particular
when implementing some container operations in terms of relocation.
This is effectively adding a library emulation of P2786R12's
is_replaceable trait, similarly to what we do for trivial relocation.
Eventually, we can replace this library emulation by the real
compiler-backed trait.
This is building towards #129328.
Diffstat (limited to 'libcxx/include/tuple')
| -rw-r--r-- | libcxx/include/tuple | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/libcxx/include/tuple b/libcxx/include/tuple index f6062891823d..8dd62ae624f5 100644 --- a/libcxx/include/tuple +++ b/libcxx/include/tuple @@ -250,6 +250,7 @@ template <class... Types> # include <__type_traits/is_nothrow_assignable.h> # include <__type_traits/is_nothrow_constructible.h> # include <__type_traits/is_reference.h> +# include <__type_traits/is_replaceable.h> # include <__type_traits/is_same.h> # include <__type_traits/is_swappable.h> # include <__type_traits/is_trivially_relocatable.h> @@ -462,8 +463,8 @@ template <class _Indx, class... _Tp> struct __tuple_impl; template <size_t... _Indx, class... _Tp> -struct _LIBCPP_DECLSPEC_EMPTY_BASES __tuple_impl<__tuple_indices<_Indx...>, _Tp...> - : public __tuple_leaf<_Indx, _Tp>... { +struct _LIBCPP_DECLSPEC_EMPTY_BASES + __tuple_impl<__tuple_indices<_Indx...>, _Tp...> : public __tuple_leaf<_Indx, _Tp>... { _LIBCPP_HIDE_FROM_ABI constexpr __tuple_impl() noexcept( __all<is_nothrow_default_constructible<_Tp>::value...>::value) {} @@ -555,6 +556,7 @@ class _LIBCPP_NO_SPECIALIZATIONS tuple { public: using __trivially_relocatable _LIBCPP_NODEBUG = __conditional_t<_And<__libcpp_is_trivially_relocatable<_Tp>...>::value, tuple, void>; + using __replaceable _LIBCPP_NODEBUG = __conditional_t<_And<__is_replaceable<_Tp>...>::value, tuple, void>; // [tuple.cnstr] |