Add merge exceptions tests for cfoa

test/Jamfile.v2

@@ -194,6 +194,7 @@ local CFOA_TESTS =
   exception_erase_tests
   exception_constructor_tests
   exception_assign_tests
+  exception_merge_tests
 ;
 
 for local test in $(CFOA_TESTS)

test/cfoa/exception_merge_tests.cpp

@@ -0,0 +1,78 @@
+// Copyright (C) 2023 Christian Mazakas
+// 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 "exception_helpers.hpp"
+
+#include <boost/unordered/concurrent_flat_map.hpp>
+
+#include <boost/core/ignore_unused.hpp>
+
+using allocator_type = stateful_allocator<std::pair<raii const, raii> >;
+
+using hasher = stateful_hash;
+using key_equal = stateful_key_equal;
+
+using map_type = boost::unordered::concurrent_flat_map<raii, raii, hasher,
+  key_equal, allocator_type>;
+
+namespace {
+  test::seed_t initialize_seed(223333016);
+
+  template <class G> void merge(G gen, test::random_generator rg)
+  {
+    auto values = make_random_values(1024 * 16, [&] { return gen(rg); });
+    auto reference_map =
+      boost::unordered_flat_map<raii, raii>(values.begin(), values.end());
+
+    raii::reset_counts();
+
+    auto begin = values.begin();
+    auto mid = begin + static_cast<std::ptrdiff_t>(values.size() / 2);
+    auto end = values.end();
+
+    {
+      unsigned num_throws = 0;
+
+      for (unsigned i = 0; i < 5 * alloc_throw_threshold; ++i) {
+        disable_exceptions();
+
+        map_type x1(0, hasher(1), key_equal(2), allocator_type(3));
+        x1.insert(begin, mid);
+
+        map_type x2(0, hasher(2), key_equal(1), allocator_type(3));
+        x2.insert(mid, end);
+
+        enable_exceptions();
+        try {
+          x1.merge(x2);
+        } catch (...) {
+          ++num_throws;
+        }
+
+        disable_exceptions();
+        test_fuzzy_matches_reference(x1, reference_map, rg);
+        test_fuzzy_matches_reference(x2, reference_map, rg);
+      }
+
+      BOOST_TEST_GT(num_throws, 0u);
+    }
+
+    check_raii_counts();
+  }
+
+} // namespace
+
+using test::default_generator;
+using test::limited_range;
+using test::sequential;
+
+// clang-format off
+UNORDERED_TEST(
+  merge,
+  ((exception_value_type_generator))
+  ((default_generator)(sequential)(limited_range)))
+
+// clang-format on
+
+RUN_TESTS()