[PATCH] libstdc++: Implement LWG 3470 change to ranges::subrange
Patrick Palka
ppalka@redhat.com
Tue Oct 19 18:29:15 GMT 2021
Tested on x86_64-pc-linux-gnu, does this look OK for trunk and branches?
libstdc++-v3/ChangeLog:
* include/bits/ranges_util.h
(__detail::__uses_nonqualification_pointer_conversion): Define
and use it ...
(__convertible_to_nonslicing): ... here, as per LWG 3470.
* testsuite/std/ranges/subrange/1.cc: New test.
---
libstdc++-v3/include/bits/ranges_util.h | 13 +++++++++----
.../testsuite/std/ranges/subrange/1.cc | 19 +++++++++++++++++++
2 files changed, 28 insertions(+), 4 deletions(-)
create mode 100644 libstdc++-v3/testsuite/std/ranges/subrange/1.cc
diff --git a/libstdc++-v3/include/bits/ranges_util.h b/libstdc++-v3/include/bits/ranges_util.h
index 7e7b958d274..765848e327d 100644
--- a/libstdc++-v3/include/bits/ranges_util.h
+++ b/libstdc++-v3/include/bits/ranges_util.h
@@ -184,11 +184,16 @@ namespace ranges
namespace __detail
{
- template<class _From, class _To>
+ template<typename _From, typename _To>
+ concept __uses_nonqualification_pointer_conversion
+ = is_pointer_v<_From> && is_pointer_v<_To>
+ && !convertible_to<remove_pointer_t<_From>(*)[],
+ remove_pointer_t<_To>(*)[]>;
+
+ template<typename _From, typename _To>
concept __convertible_to_non_slicing = convertible_to<_From, _To>
- && !(is_pointer_v<decay_t<_From>> && is_pointer_v<decay_t<_To>>
- && __different_from<remove_pointer_t<decay_t<_From>>,
- remove_pointer_t<decay_t<_To>>>);
+ && !__uses_nonqualification_pointer_conversion<decay_t<_From>,
+ decay_t<_To>>;
template<typename _Tp>
concept __pair_like
diff --git a/libstdc++-v3/testsuite/std/ranges/subrange/1.cc b/libstdc++-v3/testsuite/std/ranges/subrange/1.cc
new file mode 100644
index 00000000000..8a53261c78c
--- /dev/null
+++ b/libstdc++-v3/testsuite/std/ranges/subrange/1.cc
@@ -0,0 +1,19 @@
+// { dg-options "-std=gnu++20" }
+// { dg-do run { target c++20 } }
+
+#include <ranges>
+
+void
+test01()
+{
+ // LWG 3470
+ int a[3] = {1,2,3};
+ int* b[3] = {&a[2], &a[0], &a[1]};
+ auto c = std::ranges::subrange<const int*const*>(b);
+}
+
+int
+main()
+{
+ test01();
+}
--
2.33.1.711.g9d530dc002
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