As preparation for implementing std::constant_wrapper that's part of the
C++26 version of the <type_traits> header, the two classes _Index_tuple
and _Build_index_tuple are moved to <type_traits>. These two helpers are
needed by std::constant_wrapper to initialize the elements of one C
array with another.
Since, <bits/utility.h> already includes <type_traits> this solution
avoids creating a very small header file for just these two internal
classes. This approach doesn't move std::index_sequence and related code
to <type_traits> and therefore doesn't change which headers provide
user-facing features.
libstdc++-v3/ChangeLog:
* include/bits/utility.h (_Index_tuple): Move to <type_traits>.
(_Build_index_tuple): Ditto.
* include/std/type_traits (_Index_tuple): Ditto.
(_Build_index_tuple): Ditto.
Signed-off-by: Luc Grosheintz <luc.groshei...@gmail.com>
---
libstdc++-v3/include/bits/utility.h | 20 --------------------
libstdc++-v3/include/std/type_traits | 22 ++++++++++++++++++++++
2 files changed, 22 insertions(+), 20 deletions(-)
diff --git a/libstdc++-v3/include/bits/utility.h
b/libstdc++-v3/include/bits/utility.h
index 84d25e0c658..4e574658eba 100644
--- a/libstdc++-v3/include/bits/utility.h
+++ b/libstdc++-v3/include/bits/utility.h
@@ -137,26 +137,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
using tuple_element_t = typename tuple_element<__i, _Tp>::type;
#endif
- // Stores a tuple of indices. Used by tuple and pair, and by bind() to
- // extract the elements in a tuple.
- template<size_t... _Indexes> struct _Index_tuple { };
-
- // Builds an _Index_tuple<0, 1, 2, ..., _Num-1>.
- template<size_t _Num>
- struct _Build_index_tuple
- {
-#if __has_builtin(__make_integer_seq)
- template<typename, size_t... _Indices>
- using _IdxTuple = _Index_tuple<_Indices...>;
-
- // Clang defines __make_integer_seq for this purpose.
- using __type = __make_integer_seq<_IdxTuple, size_t, _Num>;
-#else
- // For GCC and other compilers, use __integer_pack instead.
- using __type = _Index_tuple<__integer_pack(_Num)...>;
-#endif
- };
-
#ifdef __glibcxx_integer_sequence // C++ >= 14
/// Class template integer_sequence
diff --git a/libstdc++-v3/include/std/type_traits
b/libstdc++-v3/include/std/type_traits
index ff23544fbf0..4636457eb5a 100644
--- a/libstdc++-v3/include/std/type_traits
+++ b/libstdc++-v3/include/std/type_traits
@@ -4280,6 +4280,28 @@ template<typename _Ret, typename _Fn, typename... _Args>
#endif // C++2a
+#if __cplusplus >= 201103L
+ // Stores a tuple of indices. Used by tuple and pair, and by bind() to
+ // extract the elements in a tuple.
+ template<size_t... _Indexes> struct _Index_tuple { };
+
+ // Builds an _Index_tuple<0, 1, 2, ..., _Num-1>.
+ template<size_t _Num>
+ struct _Build_index_tuple
+ {
+#if __has_builtin(__make_integer_seq)
+ template<typename, size_t... _Indices>
+ using _IdxTuple = _Index_tuple<_Indices...>;
+
+ // Clang defines __make_integer_seq for this purpose.
+ using __type = __make_integer_seq<_IdxTuple, size_t, _Num>;
+#else
+ // For GCC and other compilers, use __integer_pack instead.
+ using __type = _Index_tuple<__integer_pack(_Num)...>;
+#endif
+ };
+#endif // C++11
+
/// @} group metaprogramming
_GLIBCXX_END_NAMESPACE_VERSION
--
2.51.0
