Add explicit allocator constructor

include/boost/unordered/concurrent_flat_map.hpp

@@ -182,6 +182,11 @@ namespace boost {
       {
       }
 
+      explicit concurrent_flat_map(allocator_type a)
+          : table_(detail::foa::default_bucket_count, hasher(), key_equal(), a)
+      {
+      }
+
       /// Capacity
       ///
 

test/cfoa/constructor_tests.cpp

@@ -312,7 +312,7 @@ namespace {
       map_type x(values.begin(), values.end(), 0, hasher(1), key_equal(2),
         allocator_type{});
 
-      std::atomic_int num_transfers{0};
+      std::atomic_uint num_transfers{0};
 
       thread_runner(
         values, [&x, &reference_map, &num_transfers](
@@ -429,6 +429,21 @@ namespace {
     check_raii_counts();
   }
 
+  UNORDERED_AUTO_TEST (explicit_allocator) {
+    raii::reset_counts();
+
+    {
+      allocator_type a;
+      map_type x(a);
+
+      BOOST_TEST_EQ(x.size(), 0u);
+      BOOST_TEST_EQ(x.hash_function(), hasher());
+      BOOST_TEST_EQ(x.key_eq(), key_equal());
+
+      BOOST_TEST(x.get_allocator() == a);
+    }
+  }
+
 } // namespace
 
 // clang-format off