[committed] libstdc++: Make copyable-box completely constexpr (LWG 3572)
Commit Message
Tested powerpc64le-linux. Pushed to trunk.
This LWG issue was approved at the October 2021 plenary and can be
implemented now that std::optional is fully constexpr.
libstdc++-v3/ChangeLog:
* include/std/ranges (ranges::__detail::__box): Add constexpr to
assignment operators (LWG 3572).
* testsuite/std/ranges/adaptors/filter.cc: Check assignment of a
view that uses copyable-box.
---
libstdc++-v3/include/std/ranges | 5 ++--
.../testsuite/std/ranges/adaptors/filter.cc | 28 +++++++++++++++++++
2 files changed, 31 insertions(+), 2 deletions(-)
@@ -109,7 +109,8 @@ namespace ranges
// _GLIBCXX_RESOLVE_LIB_DEFECTS
// 3477. Simplify constraints for semiregular-box
- __box&
+ // 3572. copyable-box should be fully constexpr
+ constexpr __box&
operator=(const __box& __that)
noexcept(is_nothrow_copy_constructible_v<_Tp>)
requires (!copyable<_Tp>)
@@ -124,7 +125,7 @@ namespace ranges
return *this;
}
- __box&
+ constexpr __box&
operator=(__box&& __that)
noexcept(is_nothrow_move_constructible_v<_Tp>)
requires (!movable<_Tp>)
@@ -140,6 +140,33 @@ test06()
static_assert(!requires { views::all | filter; });
}
+constexpr bool
+test07()
+{
+ struct Pred
+ {
+ constexpr Pred() { }
+ constexpr Pred(const Pred&) { }
+ constexpr Pred(Pred&&) { }
+ // These make it non-copyable, so non-copyable-box<Pred> will provide
+ // assignment.
+ Pred& operator=(const Pred&) = delete;
+ Pred& operator=(Pred&&) = delete;
+
+ bool operator()(int i) const { return i < 10; }
+ };
+
+ int i = 0;
+ ranges::filter_view v(views::single(i), Pred{});
+ // LWG 3572. copyable-box should be fully constexpr
+ v = v;
+ v = std::move(v);
+
+ return true;
+}
+
+static_assert( test07() );
+
int
main()
{
@@ -150,4 +177,5 @@ main()
test05<forward_iterator_wrapper>();
test05<random_access_iterator_wrapper>();
test06();
+ test07();
}