[gcc r12-4078] libstdc++: Implement LWG 3529 for std::priority_queue

[Jonathan Wakely]

https://gcc.gnu.org/g:e79bde6ada42a47b0a266f1cc85efb2eed44e45a

commit r12-4078-ge79bde6ada42a47b0a266f1cc85efb2eed44e45a
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Thu May 13 14:30:26 2021 +0100

    libstdc++: Implement LWG 3529 for std::priority_queue
    
    The LWG 3529 issue changes to use two overloads instead of one with a
    default argument, so that the sequence can be initialized directly with
    the iterator range when no sequence argument is provided.
    
    Signed-off-by: Jonathan Wakely <jwakely@redhat.com>
    
    libstdc++-v3/ChangeLog:
    
            * include/bits/stl_queue.h (priority_queue): Construct sequence
            from iterators when no sequence argument is present (LWG 3529).
            * testsuite/23_containers/priority_queue/lwg3529.cc: New test.

Diff:
---
 libstdc++-v3/include/bits/stl_queue.h                     | 15 +++++++++++----
 .../testsuite/23_containers/priority_queue/lwg3529.cc     | 13 +++++++++++++
 2 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/libstdc++-v3/include/bits/stl_queue.h b/libstdc++-v3/include/bits/stl_queue.h
index 5e7808c0247..f801ebda77f 100644
--- a/libstdc++-v3/include/bits/stl_queue.h
+++ b/libstdc++-v3/include/bits/stl_queue.h
@@ -594,13 +594,21 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	  std::make_heap(c.begin(), c.end(), comp);
 	}
 #else
+      // _GLIBCXX_RESOLVE_LIB_DEFECTS
+      // 3529. priority_queue(first, last) should construct c with (first, last)
+      template<typename _InputIterator,
+	       typename = std::_RequireInputIter<_InputIterator>>
+	priority_queue(_InputIterator __first, _InputIterator __last,
+		       const _Compare& __x = _Compare())
+	: c(__first, __last), comp(__x)
+	{ std::make_heap(c.begin(), c.end(), comp); }
+
       // _GLIBCXX_RESOLVE_LIB_DEFECTS
       // 3522. Missing requirement on InputIterator template parameter
       template<typename _InputIterator,
 	       typename = std::_RequireInputIter<_InputIterator>>
 	priority_queue(_InputIterator __first, _InputIterator __last,
-		       const _Compare& __x,
-		       const _Sequence& __s)
+		       const _Compare& __x, const _Sequence& __s)
 	: c(__s), comp(__x)
 	{
 	  __glibcxx_requires_valid_range(__first, __last);
@@ -611,8 +619,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       template<typename _InputIterator,
 	       typename = std::_RequireInputIter<_InputIterator>>
 	priority_queue(_InputIterator __first, _InputIterator __last,
-		       const _Compare& __x = _Compare(),
-		       _Sequence&& __s = _Sequence())
+		       const _Compare& __x, _Sequence&& __s)
 	: c(std::move(__s)), comp(__x)
 	{
 	  __glibcxx_requires_valid_range(__first, __last);
diff --git a/libstdc++-v3/testsuite/23_containers/priority_queue/lwg3529.cc b/libstdc++-v3/testsuite/23_containers/priority_queue/lwg3529.cc
new file mode 100644
index 00000000000..014b5aa0f35
--- /dev/null
+++ b/libstdc++-v3/testsuite/23_containers/priority_queue/lwg3529.cc
@@ -0,0 +1,13 @@
+// { dg-do compile { target c++11 } }
+
+#include <queue>
+
+struct C : std::vector<int>
+{
+  C(int*, int*) { }
+};
+
+int i;
+
+// LWG 3529. priority_queue(first, last) should construct c with (first, last)
+std::priority_queue<int, C> q(&i, &i);