[libc++] Use addressof in vector.

[Mordante]

Summary

This addresses the usage of operator& in <vector>.

I now added tests for the current offending cases. I wonder whether it
would be better to add one addressof test per directory and test all
possible violations. Also to guard against possible future errors?

(Note there are still more headers with the same issue.)

[• Quuxplusone]

LprettyGTM! You'll need to #include <__memory/addressof.h> in at least one, maybe two, places, before CI will be happy.

libcxx/include/vector

1742

Pre-existing: iterator, iterator should be iterator, iterator (but that'll require updating tests, and should be a separate commit anyway)

[ldionne]

I now added tests for the current offending cases. I wonder whether it would be better to add one addressof test per directory and test all possible violations.

I won't say "no" to additional test coverage, but that sounds like a lot of work for not necessarily that much benefit. If you want to do it, then sure, but there will be a ton of stuff to check.

Whether or not we decide to expand the testing of addressof, I'm fine with this patch. Thanks for tackling this!

[needs CI to pass, as usual]

[Mordante]

Adds a missing include.

[Mordante]

For now I keep the minimal set of tests; there are still quite some headers to review left ;-)

libcxx/include/vector

1742

I created D112231, it seems not to affect tests.

libcxx/include/__iterator/wrap_iter.h

 // -*- C++ -*-
 //===----------------------------------------------------------------------===//
 //
 // 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
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef _LIBCPP___ITERATOR_WRAP_ITER_H
 #define _LIBCPP___ITERATOR_WRAP_ITER_H
 
 #include <__config>
 #include <__debug>
 #include <__iterator/iterator_traits.h>
+#include <__memory/addressof.h>
 #include <__memory/pointer_traits.h>
 #include <type_traits>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD

 #endif
     }
     template <class _Up> _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_IF_NODEBUG
         __wrap_iter(const __wrap_iter<_Up>& __u,
             typename enable_if<is_convertible<_Up, iterator_type>::value>::type* = nullptr) _NOEXCEPT
             : __i(__u.base())
     {
 #if _LIBCPP_DEBUG_LEVEL == 2
-        __get_db()->__iterator_copy(this, &__u);
+        __get_db()->__iterator_copy(this, _VSTD::addressof(__u));
 #endif
     }
 #if _LIBCPP_DEBUG_LEVEL == 2
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_IF_NODEBUG
     __wrap_iter(const __wrap_iter& __x)
         : __i(__x.base())
     {
-        __get_db()->__iterator_copy(this, &__x);
+        __get_db()->__iterator_copy(this, _VSTD::addressof(__x));
     }
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_IF_NODEBUG
     __wrap_iter& operator=(const __wrap_iter& __x)
     {
-        if (this != &__x)
+        if (this != _VSTD::addressof(__x))
         {
-            __get_db()->__iterator_copy(this, &__x);
+            __get_db()->__iterator_copy(this, _VSTD::addressof(__x));
             __i = __x.__i;
         }
         return *this;
     }
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_IF_NODEBUG
     ~__wrap_iter()
     {
         __get_db()->__erase_i(this);
bool operator==(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter2>& __y) _NOEXCEPT
     return __x.base() == __y.base();
 }
 
 template <class _Iter1>
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_IF_NODEBUG
 bool operator<(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter1>& __y) _NOEXCEPT
 {
 #if _LIBCPP_DEBUG_LEVEL == 2
-    _LIBCPP_ASSERT(__get_const_db()->__less_than_comparable(&__x, &__y),
+    _LIBCPP_ASSERT(__get_const_db()->__less_than_comparable(_VSTD::addressof(__x), _VSTD::addressof(__y)),
                    "Attempted to compare incomparable iterators");
 #endif
     return __x.base() < __y.base();
 }
 
 template <class _Iter1, class _Iter2>
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_IF_NODEBUG
 bool operator<(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter2>& __y) _NOEXCEPT

 auto operator-(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter2>& __y) _NOEXCEPT
     -> decltype(__x.base() - __y.base())
 #else
 typename __wrap_iter<_Iter1>::difference_type
 operator-(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter2>& __y) _NOEXCEPT
 #endif // C++03
 {
 #if _LIBCPP_DEBUG_LEVEL == 2
-    _LIBCPP_ASSERT(__get_const_db()->__less_than_comparable(&__x, &__y),
+    _LIBCPP_ASSERT(__get_const_db()->__less_than_comparable(_VSTD::addressof(__x), _VSTD::addressof(__y)),
                    "Attempted to subtract incompatible iterators");
 #endif
     return __x.base() - __y.base();
 }
 
 template <class _Iter1>
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_IF_NODEBUG
 __wrap_iter<_Iter1> operator+(typename __wrap_iter<_Iter1>::difference_type __n, __wrap_iter<_Iter1> __x) _NOEXCEPT

libcxx/include/vector

#if _LIBCPP_STD_VER > 14
         _NOEXCEPT
 #else
         _NOEXCEPT_(is_nothrow_move_constructible<allocator_type>::value)
 #endif
     : __base(_VSTD::move(__x.__alloc()))
 {
 #if _LIBCPP_DEBUG_LEVEL == 2
     __get_db()->__insert_c(this);
-    __get_db()->swap(this, &__x);
+    __get_db()->swap(this, _VSTD::addressof(__x));
 #endif
     this->__begin_ = __x.__begin_;
     this->__end_ = __x.__end_;
     this->__end_cap() = __x.__end_cap();
     __x.__begin_ = __x.__end_ = __x.__end_cap() = nullptr;
 }
 
 template <class _Tp, class _Allocator>
 inline _LIBCPP_INLINE_VISIBILITY
 vector<_Tp, _Allocator>::vector(vector&& __x, const __identity_t<allocator_type>& __a)
     : __base(__a)
 {
 #if _LIBCPP_DEBUG_LEVEL == 2
     __get_db()->__insert_c(this);
 #endif
     if (__a == __x.__alloc())
     {
         this->__begin_ = __x.__begin_;
         this->__end_ = __x.__end_;
         this->__end_cap() = __x.__end_cap();
         __x.__begin_ = __x.__end_ = __x.__end_cap() = nullptr;
 #if _LIBCPP_DEBUG_LEVEL == 2
-        __get_db()->swap(this, &__x);
+        __get_db()->swap(this, _VSTD::addressof(__x));
 #endif
     }
     else
     {
         typedef move_iterator<iterator> _Ip;
         assign(_Ip(__x.begin()), _Ip(__x.end()));
     }
 }

 {
     __vdeallocate();
     __base::__move_assign_alloc(__c); // this can throw
     this->__begin_ = __c.__begin_;
     this->__end_ = __c.__end_;
     this->__end_cap() = __c.__end_cap();
     __c.__begin_ = __c.__end_ = __c.__end_cap() = nullptr;
 #if _LIBCPP_DEBUG_LEVEL == 2
-    __get_db()->swap(this, &__c);
+    __get_db()->swap(this, _VSTD::addressof(__c));
 #endif
 }
 
 #endif // !_LIBCPP_CXX03_LANG
 
 template <class _Tp, class _Allocator>
 inline _LIBCPP_INLINE_VISIBILITY
 vector<_Tp, _Allocator>&

 }
 
 template <class _Tp, class _Allocator>
 inline _LIBCPP_INLINE_VISIBILITY
 typename vector<_Tp, _Allocator>::iterator
 vector<_Tp, _Allocator>::erase(const_iterator __position)
 {
 #if _LIBCPP_DEBUG_LEVEL == 2
-    _LIBCPP_ASSERT(__get_const_db()->__find_c_from_i(&__position) == this,
+    _LIBCPP_ASSERT(__get_const_db()->__find_c_from_i(_VSTD::addressof(__position)) == this,
         "vector::erase(iterator) called with an iterator not"
         " referring to this vector");
 #endif
     _LIBCPP_ASSERT(__position != end(),
         "vector::erase(iterator) called with a non-dereferenceable iterator");
     difference_type __ps = __position - cbegin();
     pointer __p = this->__begin_ + __ps;
     this->__destruct_at_end(_VSTD::move(__p + 1, this->__end_, __p));
     this->__invalidate_iterators_past(__p-1);
     iterator __r = __make_iter(__p);
     return __r;
 }
 
 template <class _Tp, class _Allocator>
 typename vector<_Tp, _Allocator>::iterator
 vector<_Tp, _Allocator>::erase(const_iterator __first, const_iterator __last)
 {
 #if _LIBCPP_DEBUG_LEVEL == 2
-    _LIBCPP_ASSERT(__get_const_db()->__find_c_from_i(&__first) == this,
+    _LIBCPP_ASSERT(__get_const_db()->__find_c_from_i(_VSTD::addressof(__first)) == this,
         "vector::erase(iterator,  iterator) called with an iterator not"
         " referring to this vector");
-    _LIBCPP_ASSERT(__get_const_db()->__find_c_from_i(&__last) == this,
+    _LIBCPP_ASSERT(__get_const_db()->__find_c_from_i(_VSTD::addressof(__last)) == this,
         "vector::erase(iterator,  iterator) called with an iterator not"
         " referring to this vector");
 #endif
     _LIBCPP_ASSERT(__first <= __last, "vector::erase(first, last) called with invalid range");
     pointer __p = this->__begin_ + (__first - begin());
     if (__first != __last) {
         this->__destruct_at_end(_VSTD::move(__p + (__last - __first), this->__end_, __p));
         this->__invalidate_iterators_past(__p - 1);
     }
vector<_Tp, _Allocator>::__move_range(pointer __from_s, pointer __from_e, pointer __to)
     _VSTD::move_backward(__from_s, __from_s + __n, __old_last);
 }
 
 template <class _Tp, class _Allocator>
 typename vector<_Tp, _Allocator>::iterator
 vector<_Tp, _Allocator>::insert(const_iterator __position, const_reference __x)
 {
 #if _LIBCPP_DEBUG_LEVEL == 2
-    _LIBCPP_ASSERT(__get_const_db()->__find_c_from_i(&__position) == this,
+    _LIBCPP_ASSERT(__get_const_db()->__find_c_from_i(_VSTD::addressof(__position)) == this,
         "vector::insert(iterator, x) called with an iterator not"
         " referring to this vector");
 #endif
     pointer __p = this->__begin_ + (__position - begin());
     if (this->__end_ < this->__end_cap())
     {
         if (__p == this->__end_)
         {

 
 #ifndef _LIBCPP_CXX03_LANG
 
 template <class _Tp, class _Allocator>
 typename vector<_Tp, _Allocator>::iterator
 vector<_Tp, _Allocator>::insert(const_iterator __position, value_type&& __x)
 {
 #if _LIBCPP_DEBUG_LEVEL == 2
-    _LIBCPP_ASSERT(__get_const_db()->__find_c_from_i(&__position) == this,
+    _LIBCPP_ASSERT(__get_const_db()->__find_c_from_i(_VSTD::addressof(__position)) == this,
         "vector::insert(iterator, x) called with an iterator not"
         " referring to this vector");
 #endif
     pointer __p = this->__begin_ + (__position - begin());
     if (this->__end_ < this->__end_cap())
     {
         if (__p == this->__end_)
         {

 }
 
 template <class _Tp, class _Allocator>
 template <class... _Args>
 typename vector<_Tp, _Allocator>::iterator
 vector<_Tp, _Allocator>::emplace(const_iterator __position, _Args&&... __args)
 {
 #if _LIBCPP_DEBUG_LEVEL == 2
-    _LIBCPP_ASSERT(__get_const_db()->__find_c_from_i(&__position) == this,
+    _LIBCPP_ASSERT(__get_const_db()->__find_c_from_i(_VSTD::addressof(__position)) == this,
         "vector::emplace(iterator, x) called with an iterator not"
         " referring to this vector");
 #endif
     pointer __p = this->__begin_ + (__position - begin());
     if (this->__end_ < this->__end_cap())
     {
         if (__p == this->__end_)
         {

 
 #endif // !_LIBCPP_CXX03_LANG
 
 template <class _Tp, class _Allocator>
 typename vector<_Tp, _Allocator>::iterator
 vector<_Tp, _Allocator>::insert(const_iterator __position, size_type __n, const_reference __x)
 {
 #if _LIBCPP_DEBUG_LEVEL == 2
-    _LIBCPP_ASSERT(__get_const_db()->__find_c_from_i(&__position) == this,
+    _LIBCPP_ASSERT(__get_const_db()->__find_c_from_i(_VSTD::addressof(__position)) == this,
         "vector::insert(iterator, n, x) called with an iterator not"
         " referring to this vector");
 #endif
     pointer __p = this->__begin_ + (__position - begin());
     if (__n > 0)
     {
         if (__n <= static_cast<size_type>(this->__end_cap() - this->__end_))
         {
<
     is_constructible<
        _Tp,
        typename iterator_traits<_InputIterator>::reference>::value,
     typename vector<_Tp, _Allocator>::iterator
 >::type
 vector<_Tp, _Allocator>::insert(const_iterator __position, _InputIterator __first, _InputIterator __last)
 {
 #if _LIBCPP_DEBUG_LEVEL == 2
-    _LIBCPP_ASSERT(__get_const_db()->__find_c_from_i(&__position) == this,
+    _LIBCPP_ASSERT(__get_const_db()->__find_c_from_i(_VSTD::addressof(__position)) == this,
         "vector::insert(iterator, range) called with an iterator not"
         " referring to this vector");
 #endif
     difference_type __off = __position - begin();
     pointer __p = this->__begin_ + __off;
     allocator_type& __a = this->__alloc();
     pointer __old_last = this->__end_;
     for (; this->__end_ != this->__end_cap() && __first != __last; ++__first)
<
     is_constructible<
        _Tp,
        typename iterator_traits<_ForwardIterator>::reference>::value,
     typename vector<_Tp, _Allocator>::iterator
 >::type
 vector<_Tp, _Allocator>::insert(const_iterator __position, _ForwardIterator __first, _ForwardIterator __last)
 {
 #if _LIBCPP_DEBUG_LEVEL == 2
-    _LIBCPP_ASSERT(__get_const_db()->__find_c_from_i(&__position) == this,
+    _LIBCPP_ASSERT(__get_const_db()->__find_c_from_i(_VSTD::addressof(__position)) == this,
         "vector::insert(iterator, range) called with an iterator not"
         " referring to this vector");
 #endif
     pointer __p = this->__begin_ + (__position - begin());
     difference_type __n = _VSTD::distance(__first, __last);
     if (__n > 0)
     {
         if (__n <= this->__end_cap() - this->__end_)
_LIBCPP_ASSERT(__alloc_traits::propagate_on_container_swap::value ||
                    "vector::swap: Either propagate_on_container_swap must be true"
                    " or the allocators must compare equal");
     _VSTD::swap(this->__begin_, __x.__begin_);
     _VSTD::swap(this->__end_, __x.__end_);
     _VSTD::swap(this->__end_cap(), __x.__end_cap());
     _VSTD::__swap_allocator(this->__alloc(), __x.__alloc(),
         integral_constant<bool,__alloc_traits::propagate_on_container_swap::value>());
 #if _LIBCPP_DEBUG_LEVEL == 2
-    __get_db()->swap(this, &__x);
+    __get_db()->swap(this, _VSTD::addressof(__x));
 #endif
 }
 
 template <class _Tp, class _Allocator>
 bool
 vector<_Tp, _Allocator>::__invariants() const
 {
     if (this->__begin_ == nullptr)

libcxx/test/std/containers/sequences/vector/vector.cons/assign_move.addressof.compile.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// <vector>
+
+// vector& operator=(vector&& c);
+
+// Validate whether the container can be copy-assigned with an ADL-hijacking operator&
+
+#include <vector>
+
+#include "test_macros.h"
+#include "operator_hijacker.h"
+
+void test() {
+  std::vector<operator_hijacker> vo;
+  std::vector<operator_hijacker> v;
+  v = std::move(vo);
+}

libcxx/test/std/containers/sequences/vector/vector.cons/move.addressof.compile.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+// 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
+
+// <vector>
+
+// vector(vector&& c);
+
+// Validate whether the container can be copy-assigned with an ADL-hijacking operator&
+
+#include <vector>
+
+#include "test_macros.h"
+#include "operator_hijacker.h"
+
+void test() {
+  {
+    std::vector<operator_hijacker> vo{};
+    std::vector<operator_hijacker> v{std::move(vo)};
+  }
+  {
+    std::vector<operator_hijacker> vo{};
+    std::vector<operator_hijacker> v{std::move(vo), std::allocator<operator_hijacker>{}};
+  }
+}

libcxx/test/std/containers/sequences/vector/vector.modifiers/emplace.addressof.compile.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+// 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
+
+// <vector>
+
+// template <class... Args> iterator emplace(const_iterator pos, Args&&... args);
+
+// Validate whether the container can be copy-assigned with an ADL-hijacking operator&
+
+#include <vector>
+
+#include "test_macros.h"
+#include "operator_hijacker.h"
+
+void test() {
+  std::vector<operator_hijacker> v;
+  v.emplace(v.end());
+}

libcxx/test/std/containers/sequences/vector/vector.modifiers/erase_iter.addressof.compile.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// <vector>
+
+// iterator erase(const_iterator position);
+
+// Validate whether the container can be copy-assigned with an ADL-hijacking operator&
+
+#include <vector>
+
+#include "test_macros.h"
+#include "operator_hijacker.h"
+
+void test() {
+  std::vector<operator_hijacker> v;
+  v.erase(v.end());
+}

libcxx/test/std/containers/sequences/vector/vector.modifiers/erase_iter_iter.addressof.compile.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// <vector>
+
+// iterator erase(const_iterator position);
+
+// Validate whether the container can be copy-assigned with an ADL-hijacking operator&
+
+#include <vector>
+
+#include "test_macros.h"
+#include "operator_hijacker.h"
+
+void test() {
+  std::vector<operator_hijacker> v;
+  v.erase(v.begin(), v.end());
+}

libcxx/test/std/containers/sequences/vector/vector.modifiers/insert_iter_iter_iter.addressof.compile.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// <vector>
+
+// template <class Iter>
+//   iterator insert(const_iterator position, Iter first, Iter last);
+
+// Validate whether the container can be copy-assigned with an ADL-hijacking operator&
+
+#include <vector>
+
+#include "test_macros.h"
+#include "operator_hijacker.h"
+#include "test_iterators.h"
+
+void test() {
+  {
+    std::vector<operator_hijacker> v;
+    cpp17_input_iterator<std::vector<operator_hijacker>::iterator> i;
+    v.insert(v.end(), i, i);
+  }
+  {
+    std::vector<operator_hijacker> v;
+    v.insert(v.end(), v.begin(), v.end());
+  }
+}

libcxx/test/std/containers/sequences/vector/vector.modifiers/insert_iter_rvalue.addressof.compile.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+// 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
+
+// <vector>
+
+// iterator insert(const_iterator position, value_type&& x);
+
+// Validate whether the container can be copy-assigned with an ADL-hijacking operator&
+
+#include <vector>
+
+#include "test_macros.h"
+#include "operator_hijacker.h"
+
+void test() {
+  std::vector<operator_hijacker> v;
+  v.insert(v.end(), operator_hijacker{});
+}

libcxx/test/std/containers/sequences/vector/vector.modifiers/insert_iter_size_value.addressof.compile.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// <vector>
+
+// iterator insert(const_iterator position, size_type n, const value_type& x);
+
+// Validate whether the container can be copy-assigned with an ADL-hijacking operator&
+
+#include <vector>
+
+#include "test_macros.h"
+#include "operator_hijacker.h"
+
+void test() {
+  std::vector<operator_hijacker> v;
+  operator_hijacker val;
+  v.insert(v.end(), 1, val);
+}

libcxx/test/std/containers/sequences/vector/vector.modifiers/insert_iter_value.addressof.compile.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// <vector>
+
+// iterator insert(const_iterator position, const value_type& x);
+
+// Validate whether the container can be copy-assigned with an ADL-hijacking operator&
+
+#include <vector>
+
+#include "test_macros.h"
+#include "operator_hijacker.h"
+
+void test() {
+  std::vector<operator_hijacker> v;
+  operator_hijacker val;
+  v.insert(v.end(), val);
+}

libcxx/test/std/containers/sequences/vector/vector.special/swap.addressof.compile.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// <vector>
+
+// template <class T, class Alloc>
+//   void swap(vector<T,Alloc>& x, vector<T,Alloc>& y);
+
+// Validate whether the container can be copy-assigned with an ADL-hijacking operator&
+
+#include <vector>
+
+#include "test_macros.h"
+#include "operator_hijacker.h"
+
+void test() {
+  std::vector<operator_hijacker> vo;
+  std::vector<operator_hijacker> v;
+  v.swap(vo);
+}