From: Patrick Palka <ppalka@redhat.com>
Date: Mon, 1 Dec 2025 22:08:01 +0000 (-0500)
Subject: libstdc++: Inconsistent const in flat_map's value_type [PR122921]
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=3e02f86cd13c787331281ab098901f8a67381945;p=thirdparty%2Fgcc.git

libstdc++: Inconsistent const in flat_map's value_type [PR122921]

flat_map's value_type is pair<key_type, mapped_type>, which we correctly
define within the container but incorrectly within the iterator.

	PR libstdc++/122921

libstdc++-v3/ChangeLog:

	* include/std/flat_map (_Flat_map_impl::_Iterator::value_type):
	Remove const from key_type to make consistent with the
	container's value_type.
	* testsuite/23_containers/flat_map/1.cc (test09): New test.
	* testsuite/23_containers/flat_multimap/1.cc (test09): New test.

Reported-by: Vincent X
Reviewed-by: Jonathan Wakely <jwakely@redhat.com>
---

diff --git a/libstdc++-v3/include/std/flat_map b/libstdc++-v3/include/std/flat_map
index de006ad1c53..e48c3eae07f 100644
--- a/libstdc++-v3/include/std/flat_map
+++ b/libstdc++-v3/include/std/flat_map
@@ -953,7 +953,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     public:
       using iterator_category = input_iterator_tag;
       using iterator_concept  = random_access_iterator_tag;
-      using value_type        = pair<const key_type, mapped_type>;
+      using value_type        = pair<key_type, mapped_type>;
       using reference         = pair<const key_type&,
 				     ranges::__maybe_const_t<_Const, mapped_type>&>;
       using difference_type   = ptrdiff_t;
diff --git a/libstdc++-v3/testsuite/23_containers/flat_map/1.cc b/libstdc++-v3/testsuite/23_containers/flat_map/1.cc
index 01278d7dc33..5bcda3464f1 100644
--- a/libstdc++-v3/testsuite/23_containers/flat_map/1.cc
+++ b/libstdc++-v3/testsuite/23_containers/flat_map/1.cc
@@ -263,6 +263,17 @@ test08()
   m[k] = 0;
 }
 
+void
+test09()
+{
+  // PR libstdc++/122921 - The value_type of flat_map's iterator should be
+  // pair<Key, T> instead of pair<const Key, T>
+  using type = std::flat_map<int, int>;
+  using value_type = std::ranges::range_value_t<type>;
+  using value_type = type::value_type;
+  using value_type = std::pair<int, int>;
+}
+
 int
 main()
 {
@@ -277,4 +288,5 @@ main()
   test06();
   test07();
   test08();
+  test09();
 }
diff --git a/libstdc++-v3/testsuite/23_containers/flat_multimap/1.cc b/libstdc++-v3/testsuite/23_containers/flat_multimap/1.cc
index d746614401d..f143f3acd1b 100644
--- a/libstdc++-v3/testsuite/23_containers/flat_multimap/1.cc
+++ b/libstdc++-v3/testsuite/23_containers/flat_multimap/1.cc
@@ -232,6 +232,17 @@ test07()
   VERIFY( std::ranges::equal(m, (std::pair<int,int>[]){{3,4},{3,3}}) );
 }
 
+void
+test09()
+{
+  // PR libstdc++/122921 - The value_type of flat_map's iterator should be
+  // pair<Key, T> instead of pair<const Key, T>
+  using type = std::flat_multimap<int, int>;
+  using value_type = std::ranges::range_value_t<type>;
+  using value_type = type::value_type;
+  using value_type = std::pair<int, int>;
+}
+
 int
 main()
 {
@@ -245,4 +256,5 @@ main()
   test05();
   test06();
   test07();
+  test09();
 }