fix: count_min_sketch allocated its hash seeds with std::allocator

count/include/count_min.hpp

@@ -382,7 +382,7 @@ class count_min_sketch{
   std::vector<W, Allocator> _sketch_array; // the array stored by the sketch
   uint64_t _seed;
   W _total_weight;
-  std::vector<uint64_t> hash_seeds;
+  std::vector<uint64_t, typename std::allocator_traits<Allocator>::template rebind_alloc<uint64_t>> hash_seeds;
 
   enum flags {IS_EMPTY};
   static const uint8_t PREAMBLE_LONGS_SHORT = 2; // Empty -> need second byte for sketch parameters

count/include/count_min_impl.hpp

@@ -38,7 +38,8 @@ _num_hashes(num_hashes),
 _num_buckets(num_buckets),
 _sketch_array((static_cast<uint64_t>(num_hashes) * num_buckets < 1<<30) ? static_cast<size_t>(num_hashes) * num_buckets : 0, 0, _allocator),
 _seed(seed),
-_total_weight(0) {
+_total_weight(0),
+hash_seeds(_allocator) {
   if (num_buckets < 3) {
     throw std::invalid_argument("Using fewer than 3 buckets incurs relative error greater than 1.");
   }

count/test/count_min_allocation_test.cpp

@@ -152,4 +152,21 @@ TEST_CASE("CountMin sketch test allocator: bytes serialize-deserialize non-empty
   REQUIRE(test_allocator_net_allocations == 0);
 }
 
+TEST_CASE("CountMin sketch test allocator: hash seeds use the sketch's allocator", "[cm_sketch_alloc]") {
+  test_allocator_total_bytes = 0;
+  test_allocator_net_allocations = 0;
+  {
+    const uint8_t n_hashes = 5;
+    const uint32_t n_buckets = 100;
+    const long long sketch_bytes = n_hashes * n_buckets * sizeof(uint64_t) + n_hashes * sizeof(uint64_t);
+    count_min_sketch_test_alloc c(n_hashes, n_buckets, DEFAULT_SEED, alloc(0));
+    // the counters and the hash seeds, all through the sketch's allocator
+    REQUIRE(test_allocator_total_bytes == sketch_bytes);
+    count_min_sketch_test_alloc copy(c);
+    REQUIRE(test_allocator_total_bytes == 2 * sketch_bytes);
+  }
+  REQUIRE(test_allocator_total_bytes == 0);
+  REQUIRE(test_allocator_net_allocations == 0);
+}
+
 } // namespace datasketches