In the P2325R3 backport r11-9555 the relaxation of the constraints on
the partial specialization of __box (which is semantically equivalent to
the primary template, only more space efficient) means some
specializations of __box will now use the partial specialization instead
of the primary template, which (IIUC) constitutes an ABI change unsuitable
for a release branch. This patch reverts this constraint change, which
isn't needed for correctness anyway.
Similarly the change to use __non_propagating_cache for the data member
split_view::_M_current (so that it's always default-initializable) also
constitutes an unsuitable ABI change. This patch reverts this change
too, and instead further constrains split_view's default constructor to
require that we can default-initialize _M_current.
PR libstdc++/103904
libstdc++-v3/ChangeLog:
* include/std/ranges (__detail::__box): Revert r11-9555 changes
to the constraints on the partial specialization and the
now-unnecessary member additions.
(__detail::__non_propagating_cache::operator=): Remove
now-unused overload added by r11-9555.
(split_view::_OuterIter::__current): Adjust after reverting the
r11-9555 change to the type of _M_current.
(split_view::_M_current): Revert r11-9555 change to its type.
(split_view::split_view): Constrain the default ctor further.
* testsuite/std/ranges/adaptors/detail/copyable_box.cc: Disable
now-irrelevant test for the r11-9555 changes to the partial
specialization of __box.
---
libstdc++-v3/include/std/ranges | 54 +++----------------
.../ranges/adaptors/detail/copyable_box.cc | 4 ++
2 files changed, 10 insertions(+), 48 deletions(-)
diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges
index 03c6275801f..bf31e4be500 100644
--- a/libstdc++-v3/include/std/ranges
+++ b/libstdc++-v3/include/std/ranges
@@ -144,8 +144,7 @@ namespace ranges
// std::optional. It provides just the subset of the primary template's
// API that we currently use.
template<__boxable _Tp>
- requires copyable<_Tp> || (is_nothrow_move_constructible_v<_Tp>
- && is_nothrow_copy_constructible_v<_Tp>)
+ requires copyable<_Tp>
struct __box<_Tp>
{
private:
@@ -174,38 +173,6 @@ namespace ranges
: _M_value(std::forward<_Args>(__args)...)
{ }
- __box(const __box&) = default;
- __box(__box&&) = default;
- __box& operator=(const __box&) requires copyable<_Tp> = default;
- __box& operator=(__box&&) requires copyable<_Tp> = default;
-
- // When _Tp is nothrow_copy_constructible but not copy_assignable,
- // copy assignment is implemented via destroy-then-copy-construct.
- constexpr __box&
- operator=(const __box& __that) noexcept
- {
- static_assert(is_nothrow_copy_constructible_v<_Tp>);
- if (this != std::__addressof(__that))
- {
- _M_value.~_Tp();
- std::construct_at(std::__addressof(_M_value), *__that);
- }
- return *this;
- }
-
- // Likewise for move assignment.
- constexpr __box&
- operator=(__box&& __that) noexcept
- {
- static_assert(is_nothrow_move_constructible_v<_Tp>);
- if (this != std::__addressof(__that))
- {
- _M_value.~_Tp();
- std::construct_at(std::__addressof(_M_value), std::move(*__that));
- }
- return *this;
- }
-
constexpr bool
has_value() const noexcept
{ return true; };
@@ -1180,16 +1147,6 @@ namespace views::__adaptor
return *this;
}
- constexpr __non_propagating_cache&
- operator=(_Tp __val)
- {
- this->_M_reset();
- std::construct_at(std::__addressof(this->_M_payload._M_payload),
- std::in_place, std::move(__val));
- this->_M_payload._M_engaged = true;
- return *this;
- }
-
constexpr _Tp&
operator*() noexcept
{ return this->_M_get(); }
@@ -2886,7 +2843,7 @@ namespace views::__adaptor
if constexpr (forward_range<_Vp>)
return _M_current;
else
- return *_M_parent->_M_current;
+ return _M_parent->_M_current;
}
constexpr auto&
@@ -2895,7 +2852,7 @@ namespace views::__adaptor
if constexpr (forward_range<_Vp>)
return _M_current;
else
- return *_M_parent->_M_current;
+ return _M_parent->_M_current;
}
_Parent* _M_parent = nullptr;
@@ -3143,13 +3100,14 @@ namespace views::__adaptor
// XXX: _M_current is "present only if !forward_range<V>"
[[no_unique_address]]
__detail::__maybe_present_t<!forward_range<_Vp>,
- __detail::__non_propagating_cache<iterator_t<_Vp>>> _M_current;
+ iterator_t<_Vp>> _M_current;
_Vp _M_base = _Vp();
public:
split_view() requires (default_initializable<_Vp>
- && default_initializable<_Pattern>)
+ && default_initializable<_Pattern>
+ && default_initializable<iterator_t<_Vp>>)
= default;
constexpr
diff --git a/libstdc++-v3/testsuite/std/ranges/adaptors/detail/copyable_box.cc
b/libstdc++-v3/testsuite/std/ranges/adaptors/detail/copyable_box.cc
index fa6d4d56816..2078d442447 100644
--- a/libstdc++-v3/testsuite/std/ranges/adaptors/detail/copyable_box.cc
+++ b/libstdc++-v3/testsuite/std/ranges/adaptors/detail/copyable_box.cc
@@ -101,6 +101,9 @@ test02()
__box<A<false>> x1(std::in_place, 0, 0);
}
+#if 0
+// On the 11 branch, the partial specialization of __box admits only copyable
types
+// so this test doesn't apply.
constexpr bool
test03()
{
@@ -142,3 +145,4 @@ test03()
return true;
}
static_assert(test03());
+#endif
--
2.35.1.102.g2b9c120970
