This issue is Tentatively Ready, and the resolution seems obviously
correct so we can do it now.
Tested powerpc64le-linux. Pushed to trunk.
-- >8 --
The _Std_pair concept uses in <bits/uses_allocator_args.h> handles const
qualified pairs, but not volatile qualified. That's because it just uses
__is_pair which is specialized for const pairs.
This removes the partial specialization __is_pair<const pair<T,U>>, so
that __is_pair is now only true for cv-unqualified pairs. Then _Std_pair
needs to explicitly use remove_cv_t for the argument to __is_pair.
The other use of __is_pair is in map::insert(Pair&&) which doesn't want
to handle volatile so should just use remove_const_t.
libstdc++-v3/ChangeLog:
* include/bits/stl_map.h (map::insert(Pair&&)): Use
remove_const_t on argument to __is_pair.
* include/bits/stl_pair.h (__is_pair<const pair<T,U>>): Remove
partial specialization.
* include/bits/uses_allocator_args.h (_Std_pair): Use
remove_cv_t as per LWG 3677.
* testsuite/20_util/uses_allocator/lwg3677.cc: New test.
---
libstdc++-v3/include/bits/stl_map.h | 2 +-
libstdc++-v3/include/bits/stl_pair.h | 3 --
.../include/bits/uses_allocator_args.h | 2 +-
.../20_util/uses_allocator/lwg3677.cc | 52 +++++++++++++++++++
4 files changed, 54 insertions(+), 5 deletions(-)
create mode 100644 libstdc++-v3/testsuite/20_util/uses_allocator/lwg3677.cc
diff --git a/libstdc++-v3/include/bits/stl_map.h
b/libstdc++-v3/include/bits/stl_map.h
index 9c2b0745673..83c579aaedc 100644
--- a/libstdc++-v3/include/bits/stl_map.h
+++ b/libstdc++-v3/include/bits/stl_map.h
@@ -847,7 +847,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
{
#if __cplusplus >= 201703L
using _P2 = remove_reference_t<_Pair>;
- if constexpr (__is_pair<_P2>)
+ if constexpr (__is_pair<remove_const_t<_P2>>)
if constexpr (is_same_v<allocator_type, allocator<value_type>>)
if constexpr (__usable_key<typename _P2::first_type>)
{
diff --git a/libstdc++-v3/include/bits/stl_pair.h
b/libstdc++-v3/include/bits/stl_pair.h
index d0f07b09d34..195167019b7 100644
--- a/libstdc++-v3/include/bits/stl_pair.h
+++ b/libstdc++-v3/include/bits/stl_pair.h
@@ -889,9 +889,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template<typename _Tp, typename _Up>
inline constexpr bool __is_pair<pair<_Tp, _Up>> = true;
-
- template<typename _Tp, typename _Up>
- inline constexpr bool __is_pair<const pair<_Tp, _Up>> = true;
#endif
/// @cond undocumented
diff --git a/libstdc++-v3/include/bits/uses_allocator_args.h
b/libstdc++-v3/include/bits/uses_allocator_args.h
index ef5c4fffb70..77e48602aac 100644
--- a/libstdc++-v3/include/bits/uses_allocator_args.h
+++ b/libstdc++-v3/include/bits/uses_allocator_args.h
@@ -44,7 +44,7 @@ namespace std _GLIBCXX_VISIBILITY(default)
_GLIBCXX_BEGIN_NAMESPACE_VERSION
template<typename _Tp>
- concept _Std_pair = __is_pair<_Tp>;
+ concept _Std_pair = __is_pair<remove_cv_t<_Tp>>;
/** @addtogroup allocators
* @{
diff --git a/libstdc++-v3/testsuite/20_util/uses_allocator/lwg3677.cc
b/libstdc++-v3/testsuite/20_util/uses_allocator/lwg3677.cc
new file mode 100644
index 00000000000..649b98d3922
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/uses_allocator/lwg3677.cc
@@ -0,0 +1,52 @@
+// { dg-options "-std=gnu++23" }
+// { dg-do run { target c++20 } }
+
+#include <memory>
+#include <testsuite_hooks.h>
+
+struct UsesAlloc
+{
+ using allocator_type = std::allocator<int>;
+
+ bool passed_alloc;
+
+ UsesAlloc(int) : passed_alloc(false) { }
+
+ UsesAlloc(int, std::allocator<int>) : passed_alloc(true) { }
+};
+
+using Pair = std::pair<UsesAlloc, int>;
+
+void
+test_const()
+{
+ std::allocator<int> a;
+ int i = 0;
+ auto p = std::make_obj_using_allocator<const Pair>(a, i, i);
+ VERIFY( p.first.passed_alloc );
+}
+
+void
+test_volatile()
+{
+ std::allocator<int> a;
+ int i = 0;
+ auto p = std::make_obj_using_allocator<volatile Pair>(a, i, i);
+ VERIFY( p.first.passed_alloc );
+}
+
+void
+test_const_volatile()
+{
+ std::allocator<int> a;
+ int i = 0;
+ auto p = std::make_obj_using_allocator<volatile Pair>(a, i, i);
+ VERIFY( p.first.passed_alloc );
+}
+
+int main()
+{
+ test_const();
+ test_volatile();
+ test_const_volatile();
+}
--
2.37.3
