[libcxx-commits] [libcxx] [libc++] Always initialize __tree::{, const_}iterator (PR #147167)

[Nikolas Klauser via libcxx-commits]

https://github.com/philnik777 created https://github.com/llvm/llvm-project/pull/147167

There doesn't seem to be much of a reason to not initialize the iterator types in all standard modes. This avoids potential reads of uninitialized memory in C++03/C++11 without any harm I can see.


>From 40673a09e6f1ce1b3e238b8ba3e258f6f6362314 Mon Sep 17 00:00:00 2001
From: Nikolas Klauser <nikolasklauser at berlin.de>
Date: Sun, 6 Jul 2025 01:26:04 +0200
Subject: [PATCH] [libc++] Always initialize __tree::{,const_}iterator

---
 libcxx/include/__tree                         | 14 ++--------
 .../map/initialize_iterator.pass.cpp          | 26 +++++++++++++++++++
 .../set/initialize_iterator.pass.cpp          | 26 +++++++++++++++++++
 3 files changed, 54 insertions(+), 12 deletions(-)
 create mode 100644 libcxx/test/libcxx/containers/associative/map/initialize_iterator.pass.cpp
 create mode 100644 libcxx/test/libcxx/containers/associative/set/initialize_iterator.pass.cpp

diff --git a/libcxx/include/__tree b/libcxx/include/__tree
index 9d4ba3ad0639c..5dee314b847f2 100644
--- a/libcxx/include/__tree
+++ b/libcxx/include/__tree
@@ -646,12 +646,7 @@ public:
   using reference         = value_type&;
   using pointer           = __rebind_pointer_t<_NodePtr, value_type>;
 
-  _LIBCPP_HIDE_FROM_ABI __tree_iterator() _NOEXCEPT
-#if _LIBCPP_STD_VER >= 14
-      : __ptr_(nullptr)
-#endif
-  {
-  }
+  _LIBCPP_HIDE_FROM_ABI __tree_iterator() _NOEXCEPT : __ptr_(nullptr) {}
 
   _LIBCPP_HIDE_FROM_ABI reference operator*() const { return __get_np()->__value_; }
   _LIBCPP_HIDE_FROM_ABI pointer operator->() const { return pointer_traits<pointer>::pointer_to(__get_np()->__value_); }
@@ -720,12 +715,7 @@ public:
   using reference         = const value_type&;
   using pointer           = __rebind_pointer_t<_NodePtr, const value_type>;
 
-  _LIBCPP_HIDE_FROM_ABI __tree_const_iterator() _NOEXCEPT
-#if _LIBCPP_STD_VER >= 14
-      : __ptr_(nullptr)
-#endif
-  {
-  }
+  _LIBCPP_HIDE_FROM_ABI __tree_const_iterator() _NOEXCEPT : __ptr_(nullptr) {}
 
 private:
   typedef __tree_iterator<_Tp, __node_pointer, difference_type> __non_const_iterator;
diff --git a/libcxx/test/libcxx/containers/associative/map/initialize_iterator.pass.cpp b/libcxx/test/libcxx/containers/associative/map/initialize_iterator.pass.cpp
new file mode 100644
index 0000000000000..cfa8e72e98e51
--- /dev/null
+++ b/libcxx/test/libcxx/containers/associative/map/initialize_iterator.pass.cpp
@@ -0,0 +1,26 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03
+
+// Check that map::iterator is initialized when default constructed
+
+#include <cassert>
+#include <map>
+
+template <class Iter>
+void test() {
+  Iter iter;
+  Iter iter2 = Iter();
+  assert(iter == iter2);
+}
+
+int main() {
+  test<std::map<int, int>::iterator>();
+  test<std::map<int, int>::const_iterator>();
+}
diff --git a/libcxx/test/libcxx/containers/associative/set/initialize_iterator.pass.cpp b/libcxx/test/libcxx/containers/associative/set/initialize_iterator.pass.cpp
new file mode 100644
index 0000000000000..c919e5c3680c3
--- /dev/null
+++ b/libcxx/test/libcxx/containers/associative/set/initialize_iterator.pass.cpp
@@ -0,0 +1,26 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03
+
+// Check that set::iterator is initialized when default constructed
+
+#include <cassert>
+#include <set>
+
+template <class Iter>
+void test() {
+  Iter iter;
+  Iter iter2 = Iter();
+  assert(iter == iter2);
+}
+
+int main() {
+  test<std::set<int>::iterator>();
+  test<std::set<int>::const_iterator>();
+}