Merge pull request #173 from cmazakas/fix/exception-guarantees

Exception Guarantees

doc/unordered/unordered_flat_map.adoc

@@ -98,9 +98,8 @@ namespace boost {
     xref:#unordered_flat_map_destructor[~unordered_flat_map]();
     unordered_flat_map& xref:#unordered_flat_map_copy_assignment[operator++=++](const unordered_flat_map& other);
     unordered_flat_map& xref:#unordered_flat_map_move_assignment[operator++=++](unordered_flat_map&& other)
-      noexcept(boost::allocator_traits<Allocator>::is_always_equal::value &&
+      noexcept(boost::allocator_traits<Allocator>::is_always_equal::value ||
-               boost::is_nothrow_move_assignable_v<Hash> &&
+              boost::allocator_traits<Allocator>::propagate_on_container_move_assignment::value);
-               boost::is_nothrow_move_assignable_v<Pred>);
     unordered_flat_map& xref:#unordered_flat_map_initializer_list_assignment[operator++=++](std::initializer_list<value_type>);
     allocator_type xref:#unordered_flat_map_get_allocator[get_allocator]() const noexcept;
 
@@ -154,9 +153,8 @@ namespace boost {
     template<class K> size_type xref:#unordered_flat_map_transparent_erase_by_key[erase](K&& k);
     iterator  xref:#unordered_flat_map_erase_range[erase](const_iterator first, const_iterator last);
     void      xref:#unordered_flat_map_swap[swap](unordered_flat_map& other)
-      noexcept(boost::allocator_traits<Allocator>::is_always_equal::value &&
+      noexcept(boost::allocator_traits<Allocator>::is_always_equal::value ||
-               boost::is_nothrow_swappable_v<Hash> &&
+               boost::allocator_traits<Allocator>::propagate_on_container_swap::value);
-               boost::is_nothrow_swappable_v<Pred>);
     void      xref:#unordered_flat_map_clear[clear]() noexcept;
 
     template<class H2, class P2>
@@ -606,11 +604,10 @@ Requires:;; `value_type` is https://en.cppreference.com/w/cpp/named_req/CopyInse
 ==== Move Assignment
 ```c++
 unordered_flat_map& operator=(unordered_flat_map&& other)
-  noexcept(boost::allocator_traits<Allocator>::is_always_equal::value &&
+  noexcept(boost::allocator_traits<Allocator>::is_always_equal::value ||
-           boost::is_nothrow_move_assignable_v<Hash> &&
+           boost::allocator_traits<Allocator>::propagate_on_container_move_assignment::value);
-           boost::is_nothrow_move_assignable_v<Pred>);
 ```
-The move assignment operator. Destroys previously existing elements, move-assigns the hash function and predicate from `other`,
+The move assignment operator. Destroys previously existing elements, swaps the hash function and predicate from `other`,
 and move-assigns the allocator from `other` if `Alloc::propagate_on_container_move_assignment` exists and `Alloc::propagate_on_container_move_assignment::value` is `true`.
 If at this point the allocator is equal to `other.get_allocator()`, the internal bucket array of `other` is transferred directly to the new container;
 otherwise, inserts move-constructed copies of the elements of `other`.
@@ -1043,9 +1040,8 @@ Throws:;; Nothing in this implementation (neither the `hasher` nor the `key_equa
 ==== swap
 ```c++
 void swap(unordered_flat_map& other)
-  noexcept(boost::allocator_traits<Allocator>::is_always_equal::value &&
+  noexcept(boost::allocator_traits<Allocator>::is_always_equal::value ||
-           boost::is_nothrow_swappable_v<Hash> &&
+           boost::allocator_traits<Allocator>::propagate_on_container_swap::value);
-           boost::is_nothrow_swappable_v<Pred>);
 ```
 
 Swaps the contents of the container with the parameter.

doc/unordered/unordered_flat_set.adoc

@@ -93,9 +93,8 @@ namespace boost {
     xref:#unordered_flat_set_destructor[~unordered_flat_set]();
     unordered_flat_set& xref:#unordered_flat_set_copy_assignment[operator++=++](const unordered_flat_set& other);
     unordered_flat_set& xref:#unordered_flat_set_move_assignment[operator++=++](unordered_flat_set&& other)
-      noexcept(boost::allocator_traits<Allocator>::is_always_equal::value &&
+      noexcept(boost::allocator_traits<Allocator>::is_always_equal::value ||
-               boost::is_nothrow_move_assignable_v<Hash> &&
+               boost::allocator_traits<Allocator>::propagate_on_container_move_assignment::value);
-               boost::is_nothrow_move_assignable_v<Pred>);
     unordered_flat_set& xref:#unordered_flat_set_initializer_list_assignment[operator++=++](std::initializer_list<value_type>);
     allocator_type xref:#unordered_flat_set_get_allocator[get_allocator]() const noexcept;
 
@@ -128,9 +127,8 @@ namespace boost {
     template<class K> size_type xref:#unordered_flat_set_transparent_erase_by_key[erase](K&& k);
     iterator  xref:#unordered_flat_set_erase_range[erase](const_iterator first, const_iterator last);
     void      xref:#unordered_flat_set_swap[swap](unordered_flat_set& other)
-      noexcept(boost::allocator_traits<Allocator>::is_always_equal::value &&
+      noexcept(boost::allocator_traits<Allocator>::is_always_equal::value ||
-               boost::is_nothrow_swappable_v<Hash> &&
+               boost::allocator_traits<Allocator>::propagate_on_container_swap::value);
-               boost::is_nothrow_swappable_v<Pred>);
     void      xref:#unordered_flat_set_clear[clear]() noexcept;
 
     template<class H2, class P2>
@@ -565,11 +563,10 @@ Requires:;; `value_type` is https://en.cppreference.com/w/cpp/named_req/CopyInse
 ==== Move Assignment
 ```c++
 unordered_flat_set& operator=(unordered_flat_set&& other)
-  noexcept(boost::allocator_traits<Allocator>::is_always_equal::value &&
+  noexcept(boost::allocator_traits<Allocator>::is_always_equal::value ||
-           boost::is_nothrow_move_assignable_v<Hash> &&
+           boost::allocator_traits<Allocator>::propagate_on_container_move_assignment::value);
-           boost::is_nothrow_move_assignable_v<Pred>);
 ```
-The move assignment operator. Destroys previously existing elements, move-assigns the hash function and predicate from `other`,
+The move assignment operator. Destroys previously existing elements, swaps the hash function and predicate from `other`,
 and move-assigns the allocator from `other` if `Alloc::propagate_on_container_move_assignment` exists and `Alloc::propagate_on_container_move_assignment::value` is `true`.
 If at this point the allocator is equal to `other.get_allocator()`, the internal bucket array of `other` is transferred directly to the new container;
 otherwise, inserts move-constructed copies of the elements of `other`.
@@ -863,9 +860,8 @@ Throws:;; Nothing in this implementation (neither the `hasher` nor the `key_equa
 ==== swap
 ```c++
 void swap(unordered_flat_set& other)
-  noexcept(boost::allocator_traits<Allocator>::is_always_equal::value &&
+  noexcept(boost::allocator_traits<Allocator>::is_always_equal::value ||
-           boost::is_nothrow_swappable_v<Hash> &&
+           boost::allocator_traits<Allocator>::propagate_on_container_swap::value);
-           boost::is_nothrow_swappable_v<Pred>);
 ```
 
 Swaps the contents of the container with the parameter.

include/boost/unordered/detail/foa.hpp

@@ -69,6 +69,12 @@
   }while(0)
 #endif
 
+#define BOOST_UNORDERED_STATIC_ASSERT_HASH_PRED(Hash, Pred)                    \
+  static_assert(boost::is_nothrow_swappable<Hash>::value,                      \
+    "Template parameter Hash is required to be nothrow Swappable.");           \
+  static_assert(boost::is_nothrow_swappable<Pred>::value,                      \
+    "Template parameter Pred is required to be nothrow Swappable");
+
 namespace boost{
 namespace unordered{
 namespace detail{
@@ -1260,13 +1266,28 @@ public:
 
   table& operator=(const table& x)
   {
+    BOOST_UNORDERED_STATIC_ASSERT_HASH_PRED(Hash, Pred)
+
     static constexpr auto pocca=
       alloc_traits::propagate_on_container_copy_assignment::value;
 
     if(this!=std::addressof(x)){
-      clear();
+      // if copy construction here winds up throwing, the container is still
-      h()=x.h();
+      // left intact so we perform these operations first
-      pred()=x.pred();
+      hasher    tmp_h=x.h();
+      key_equal tmp_p=x.pred();
+
+      // already noexcept, clear() before we swap the Hash, Pred just in case
+      // the clear() impl relies on them at some point in the future
+      clear(); 
+
+      // because we've asserted at compile-time that Hash and Pred are nothrow
+      // swappable, we can safely mutate our source container and maintain
+      // consistency between the Hash, Pred compatibility
+      using std::swap;
+      swap(h(),tmp_h);
+      swap(pred(),tmp_p);
+
       if_constexpr<pocca>([&,this]{
         if(al()!=x.al())reserve(0);
         copy_assign_if<pocca>(al(),x.al());
@@ -1285,19 +1306,32 @@ public:
 
   table& operator=(table&& x)
     noexcept(
-      alloc_traits::is_always_equal::value&&
+      alloc_traits::propagate_on_container_move_assignment::value||
-      std::is_nothrow_move_assignable<Hash>::value&&
+      alloc_traits::is_always_equal::value)
-      std::is_nothrow_move_assignable<Pred>::value)
   {
+    BOOST_UNORDERED_STATIC_ASSERT_HASH_PRED(Hash, Pred)
+
     static constexpr auto pocma=
       alloc_traits::propagate_on_container_move_assignment::value;
 
     if(this!=std::addressof(x)){
+      /* Given ambiguity in implementation strategies briefly discussed here:
+       * https://www.open-std.org/jtc1/sc22/wg21/docs/lwg-active.html#2227
+       *
+       * we opt into requiring nothrow swappability and eschew the move
+       * operations associated with Hash, Pred.
+       *
+       * To this end, we ensure that the user never has to consider the
+       * moved-from state of their Hash, Pred objects
+       */
+
+      using std::swap;
+
       clear();
-      h()=std::move(x.h());
+      swap(h(),x.h());
-      pred()=std::move(x.pred());
+      swap(pred(),x.pred());
+
       if(pocma||al()==x.al()){
-        using std::swap;
         reserve(0);
         move_assign_if<pocma>(al(),x.al());
         swap(size_,x.size_);
@@ -1412,16 +1446,15 @@ public:
 
   void swap(table& x)
     noexcept(
-      alloc_traits::is_always_equal::value&&
+      alloc_traits::propagate_on_container_swap::value||
-      boost::is_nothrow_swappable<Hash>::value&&
+      alloc_traits::is_always_equal::value)
-      boost::is_nothrow_swappable<Pred>::value)
   {
+    BOOST_UNORDERED_STATIC_ASSERT_HASH_PRED(Hash, Pred)
+
     static constexpr auto pocs=
       alloc_traits::propagate_on_container_swap::value;
 
     using std::swap;
-    swap(h(),x.h());
-    swap(pred(),x.pred());
     if_constexpr<pocs>([&,this]{
       swap_if<pocs>(al(),x.al());
     },
@@ -1429,6 +1462,9 @@ public:
       BOOST_ASSERT(al()==x.al());
       (void)this; /* makes sure captured this is used */
     });
+
+    swap(h(),x.h());
+    swap(pred(),x.pred());
     swap(size_,x.size_);
     swap(arrays,x.arrays);
     swap(ml,x.ml);
@@ -2075,6 +2111,7 @@ private:
 
 #undef BOOST_UNORDERED_ASSUME
 #undef BOOST_UNORDERED_HAS_BUILTIN
+#undef BOOST_UNORDERED_STATIC_ASSERT_HASH_PRED
 #ifdef BOOST_UNORDERED_LITTLE_ENDIAN_NEON
 #undef BOOST_UNORDERED_LITTLE_ENDIAN_NEON
 #endif

test/exception/assign_exception_tests.cpp

@@ -60,6 +60,9 @@ template <class T> struct assign_base : public test::exception_base
   test::random_values<T> x_values, y_values;
   T x, y;
 
+  int t1;
+  int t2;
+
   typedef typename T::hasher hasher;
   typedef typename T::key_equal key_equal;
   typedef typename T::allocator_type allocator_type;
@@ -67,7 +70,10 @@ template <class T> struct assign_base : public test::exception_base
   assign_base(int tag1, int tag2, float mlf1 = 1.0, float mlf2 = 1.0)
       : x_values(), y_values(),
         x(0, hasher(tag1), key_equal(tag1), allocator_type(tag1)),
-        y(0, hasher(tag2), key_equal(tag2), allocator_type(tag2))
+        y(0, hasher(tag2), key_equal(tag2), allocator_type(tag2)),
+        t1(tag1),
+        t2(tag2)
+
   {
     x.max_load_factor(mlf1);
     y.max_load_factor(mlf2);
@@ -89,6 +95,22 @@ template <class T> struct assign_base : public test::exception_base
   {
     test::check_equivalent_keys(x1);
 
+    if (x1.hash_function() == hasher(t1)) {
+      BOOST_TEST(x1.key_eq() == key_equal(t1));
+    }
+
+    if (x1.hash_function() == hasher(t2)) {
+      BOOST_TEST(x1.key_eq() == key_equal(t2));
+    }
+
+    if (x1.key_eq() == key_equal(t1)) {
+      BOOST_TEST(x1.hash_function() == hasher(t1));
+    }
+
+    if (x1.key_eq() == key_equal(t2)) {
+      BOOST_TEST(x1.hash_function() == hasher(t2));
+    }
+
     // If the container is empty at the point of the exception, the
     // internal structure is hidden, this exposes it, at the cost of
     // messing up the data.

test/exception/move_assign_exception_tests.cpp

@@ -20,6 +20,7 @@ template <class T> struct move_assign_base : public test::exception_base
 {
   test::random_values<T> x_values, y_values;
   T x, y;
+  int t1, t2;
 
   typedef typename T::hasher hasher;
   typedef typename T::key_equal key_equal;
@@ -28,7 +29,9 @@ template <class T> struct move_assign_base : public test::exception_base
   move_assign_base(int tag1, int tag2, float mlf1 = 1.0, float mlf2 = 1.0)
       : x_values(), y_values(),
         x(0, hasher(tag1), key_equal(tag1), allocator_type(tag1)),
-        y(0, hasher(tag2), key_equal(tag2), allocator_type(tag2))
+        y(0, hasher(tag2), key_equal(tag2), allocator_type(tag2)),
+        t1(tag1),
+        t2(tag2)
   {
     x.max_load_factor(mlf1);
     y.max_load_factor(mlf2);
@@ -52,6 +55,22 @@ template <class T> struct move_assign_base : public test::exception_base
   {
     test::check_equivalent_keys(x1);
 
+    if (x1.hash_function() == hasher(t1)) {
+      BOOST_TEST(x1.key_eq() == key_equal(t1));
+    }
+
+    if (x1.hash_function() == hasher(t2)) {
+      BOOST_TEST(x1.key_eq() == key_equal(t2));
+    }
+
+    if (x1.key_eq() == key_equal(t1)) {
+      BOOST_TEST(x1.hash_function() == hasher(t1));
+    }
+
+    if (x1.key_eq() == key_equal(t2)) {
+      BOOST_TEST(x1.hash_function() == hasher(t2));
+    }
+
     // If the container is empty at the point of the exception, the
     // internal structure is hidden, this exposes it, at the cost of
     // messing up the data.

test/exception/swap_exception_tests.cpp

@@ -4,15 +4,40 @@
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
 
-#include "./containers.hpp"
+#define BOOST_ENABLE_ASSERT_HANDLER
+#include <boost/assert.hpp>
 
-#if defined(BOOST_UNORDERED_FOA_TESTS)
+#include "./containers.hpp"
-#define BOOST_UNORDERED_FOA_WEAK_GUARANTEE_SWAP_EXCEPTIONS_TESTS
-#endif
 
 #include "../helpers/invariants.hpp"
 #include "../helpers/random_values.hpp"
 #include "../helpers/tracker.hpp"
+#include "../objects/test.hpp"
+
+#include <sstream>
+
+namespace boost {
+  void assertion_failed(
+    char const* expr, char const* function, char const* file, long line)
+  {
+    std::stringstream ss;
+    ss << expr << "\nin " << function << " failed at : " << file << ", line "
+       << line;
+
+    throw std::runtime_error(ss.str());
+  }
+
+  void assertion_failed_msg(char const* expr, char const* msg,
+    char const* function, char const* file, long line)
+  {
+    std::stringstream ss;
+    ss << expr << "\nin " << function << " failed at : " << file << ", line "
+       << line << "\n"
+       << msg;
+
+    throw std::runtime_error(ss.str());
+  }
+} // namespace boost
 
 #if defined(BOOST_MSVC)
 #pragma warning(disable : 4512) // assignment operator could not be generated
@@ -39,15 +64,10 @@ template <class T> struct self_swap_base : public test::exception_base
 
   void check BOOST_PREVENT_MACRO_SUBSTITUTION(T const& x) const
   {
-    std::string scope(test::scope);
+    (void)x;
 
-    // TODO: In C++11 exceptions are only allowed in the swap function.
+    BOOST_ERROR("An exception leaked when it should not have. Allocator "
-    BOOST_TEST(scope == "hash::hash(hash)" ||
+                "equality assertion must precede all other ops");
-               scope == "hash::operator=(hash)" ||
-               scope == "equal_to::equal_to(equal_to)" ||
-               scope == "equal_to::operator=(equal_to)");
-
-    test::check_equivalent_keys(x);
   }
 };
 
@@ -140,11 +160,133 @@ template <class T> struct swap_test4 : swap_base<T>
   swap_test4() : swap_base<T>(10, 10, 1, 2) {}
 };
 
+template <class T> struct unequal_alloc_swap_base : public test::exception_base
+{
+  const test::random_values<T> x_values, y_values;
+  const T initial_x, initial_y;
+
+  typedef typename T::hasher hasher;
+  typedef typename T::key_equal key_equal;
+  typedef typename T::allocator_type allocator_type;
+
+  unequal_alloc_swap_base(unsigned int count1, unsigned int count2)
+      : x_values(count1, test::limited_range),
+        y_values(count2, test::limited_range),
+        initial_x(x_values.begin(), x_values.end(), 0, allocator_type(1337)),
+        initial_y(y_values.begin(), y_values.end(), 0, allocator_type(7331))
+  {
+  }
+
+  struct data_type
+  {
+    data_type(T const& x_, T const& y_) : x(x_), y(y_) {}
+
+    T x, y;
+  };
+
+  data_type init() const { return data_type(initial_x, initial_y); }
+
+  void run(data_type& d) const
+  {
+    bool assert_threw = false;
+
+    BOOST_TEST(d.x.get_allocator() != d.y.get_allocator());
+
+    try {
+      d.x.swap(d.y);
+    } catch (std::runtime_error&) {
+      assert_threw = true;
+    }
+
+    DISABLE_EXCEPTIONS;
+    BOOST_TEST(assert_threw);
+    test::check_container(d.x, this->x_values);
+    test::check_equivalent_keys(d.x);
+    test::check_container(d.y, this->y_values);
+    test::check_equivalent_keys(d.y);
+  }
+
+  void check BOOST_PREVENT_MACRO_SUBSTITUTION(data_type const& d) const
+  {
+    std::string scope(test::scope);
+
+    // TODO: In C++11 exceptions are only allowed in the swap function.
+    BOOST_TEST(scope == "hash::hash(hash)" ||
+               scope == "hash::operator=(hash)" ||
+               scope == "equal_to::equal_to(equal_to)" ||
+               scope == "equal_to::operator=(equal_to)");
+
+    test::check_equivalent_keys(d.x);
+    test::check_equivalent_keys(d.y);
+  }
+};
+
+template <class T> struct unequal_alloc_swap_test1 : unequal_alloc_swap_base<T>
+{
+  unequal_alloc_swap_test1() : unequal_alloc_swap_base<T>(0, 0) {}
+};
+
+template <class T> struct unequal_alloc_swap_test2 : unequal_alloc_swap_base<T>
+{
+  unequal_alloc_swap_test2() : unequal_alloc_swap_base<T>(0, 10) {}
+};
+
+template <class T> struct unequal_alloc_swap_test3 : unequal_alloc_swap_base<T>
+{
+  unequal_alloc_swap_test3() : unequal_alloc_swap_base<T>(10, 0) {}
+};
+
+template <class T> struct unequal_alloc_swap_test4 : unequal_alloc_swap_base<T>
+{
+  unequal_alloc_swap_test4() : unequal_alloc_swap_base<T>(10, 10) {}
+};
+
+#if defined(BOOST_UNORDERED_FOA_TESTS)
+
+using unordered_flat_set = boost::unordered_flat_set<int, boost::hash<int>,
+  std::equal_to<int>, test::allocator1<int> >;
+using unordered_flat_map = boost::unordered_flat_map<int, int, boost::hash<int>,
+  std::equal_to<int>, test::allocator1<std::pair<int const, int> > >;
+
+#define SWAP_CONTAINER_SEQ (unordered_flat_set)(unordered_flat_map)
+
+#else
+
+typedef boost::unordered_set<int, boost::hash<int>, std::equal_to<int>,
+  test::allocator1<int> >
+  unordered_set;
+typedef boost::unordered_map<int, int, boost::hash<int>, std::equal_to<int>,
+  test::allocator1<std::pair<int const, int> > >
+  unordered_map;
+typedef boost::unordered_multiset<int, boost::hash<int>, std::equal_to<int>,
+  test::allocator1<int> >
+  unordered_multiset;
+typedef boost::unordered_multimap<int, int, boost::hash<int>,
+  std::equal_to<int>, test::allocator1<std::pair<int const, int> > >
+  unordered_multimap;
+
+#define SWAP_CONTAINER_SEQ                                                     \
+  (unordered_set)(unordered_map)(unordered_multiset)(unordered_multimap)
+#endif
+
+// FOA containers deliberately choose to not offer the strong exception
+// guarantee so we can't reliably test what happens if swapping one of the data
+// members throws
+//
 // clang-format off
+#if !defined(BOOST_UNORDERED_FOA_TESTS)
 EXCEPTION_TESTS(
   (self_swap_test1)(self_swap_test2)
   (swap_test1)(swap_test2)(swap_test3)(swap_test4),
   CONTAINER_SEQ)
+#endif
+
+// want to prove that when assertions are defined as throwing operations that we
+// uphold invariants
+EXCEPTION_TESTS(
+  (unequal_alloc_swap_test1)(unequal_alloc_swap_test2)
+  (unequal_alloc_swap_test3)(unequal_alloc_swap_test4),
+  SWAP_CONTAINER_SEQ)
 // clang-format on
 
 RUN_TESTS()

test/helpers/invariants.hpp

@@ -54,20 +54,10 @@ namespace test {
       if (test::has_unique_keys<X>::value && count != 1)
         BOOST_ERROR("Non-unique key.");
 
-#if !defined(BOOST_UNORDERED_FOA_WEAK_GUARANTEE_SWAP_EXCEPTIONS_TESTS)
-      // we conditionally compile this check because our FOA implementation only
-      // exhibits the weak guarantee when swapping throws
-      //
-      // in this case, the hasher may be changed before the predicate and the
-      // arrays are swapped in which case, we can can find an element by
-      // iteration but unfortunately, it's in the wrong slot according to the
-      // new hash function so count(key) can wind up returning nothing when
-      // there really is something
       if (x1.count(key) != count) {
         BOOST_ERROR("Incorrect output of count.");
         std::cerr << x1.count(key) << "," << count << "\n";
       }
-#endif
 
 #ifndef BOOST_UNORDERED_FOA_TESTS
       // Check that the keys are in the correct bucket and are

test/objects/exception.hpp

@@ -227,8 +227,21 @@ namespace test {
         }
         return x1.tag_ != x2.tag_;
       }
+
+#if defined(BOOST_UNORDERED_FOA_TESTS)
+      friend void swap(hash&, hash&) noexcept;
+#endif
     };
 
+#if defined(BOOST_UNORDERED_FOA_TESTS)
+      void swap(hash& lhs, hash& rhs) noexcept
+      {
+        int tag = lhs.tag_;
+        lhs.tag_ = rhs.tag_;
+        rhs.tag_ = tag;
+      }
+#endif
+
     class less
     {
       int tag_;
@@ -364,8 +377,20 @@ namespace test {
       }
 
       friend less create_compare(equal_to x) { return less(x.tag_); }
+#if defined(BOOST_UNORDERED_FOA_TESTS)
+      friend void swap(equal_to&, equal_to&) noexcept;
+#endif
     };
 
+#if defined(BOOST_UNORDERED_FOA_TESTS)
+    void swap(equal_to& lhs, equal_to& rhs) noexcept
+    {
+      int tag = lhs.tag_;
+      lhs.tag_ = rhs.tag_;
+      rhs.tag_ = tag;
+    }
+#endif
+
     template <class T> class allocator
     {
     public:

test/objects/minimal.hpp

@@ -206,6 +206,11 @@ namespace test {
       hash& operator=(hash const&) { return *this; }
       ~hash() {}
 
+#if defined(BOOST_UNORDERED_FOA_TESTS)
+      hash(hash&&) = default;
+      hash& operator=(hash&&) = default;
+#endif
+
       std::size_t operator()(T const&) const { return 0; }
 #if BOOST_UNORDERED_CHECK_ADDR_OPERATOR_NOT_USED
       ampersand_operator_used operator&() const
@@ -224,6 +229,11 @@ namespace test {
       equal_to& operator=(equal_to const&) { return *this; }
       ~equal_to() {}
 
+#if defined(BOOST_UNORDERED_FOA_TESTS)
+      equal_to(equal_to&&) = default;
+      equal_to& operator=(equal_to&&) = default;
+#endif
+
       bool operator()(T const&, T const&) const { return true; }
 #if BOOST_UNORDERED_CHECK_ADDR_OPERATOR_NOT_USED
       ampersand_operator_used operator&() const

test/unordered/noexcept_tests.cpp

@@ -437,13 +437,11 @@ UNORDERED_AUTO_TEST (prelim_allocator_checks) {
 using test::default_generator;
 
 #ifdef BOOST_UNORDERED_FOA_TESTS
-boost::unordered_flat_set<int, noexcept_tests::hash_nothrow_move_assign,
+boost::unordered_flat_set<int, noexcept_tests::hash_nothrow_swap,
-  noexcept_tests::equal_to_nothrow_move_assign, allocator1<int> >*
+  noexcept_tests::equal_to_nothrow_swap, allocator1<int> >* throwing_set_alloc1;
-  throwing_set_alloc1;
 
-boost::unordered_flat_set<int, noexcept_tests::hash_nothrow_move_assign,
+boost::unordered_flat_set<int, noexcept_tests::hash_nothrow_swap,
-  noexcept_tests::equal_to_nothrow_move_assign, allocator2<int> >*
+  noexcept_tests::equal_to_nothrow_swap, allocator2<int> >* throwing_set_alloc2;
-  throwing_set_alloc2;
 
 UNORDERED_TEST(test_nothrow_move_assign_when_noexcept,
   ((throwing_set_alloc1)(throwing_set_alloc2))((default_generator)))