fix metrics compiler warnings (open-telemetry#1328)

Author: esigo

sdk/include/opentelemetry/sdk/metrics/view/attributes_processor.h

@@ -23,6 +23,8 @@ class AttributesProcessor
   // @returns The processed attributes
   virtual MetricAttributes process(
       const opentelemetry::common::KeyValueIterable &attributes) const noexcept = 0;
+
+  virtual ~AttributesProcessor() = default;
 };
 
 /**

sdk/src/metrics/meter.cc

@@ -206,7 +206,7 @@ std::unique_ptr<WritableMetricStorage> Meter::RegisterMetricStorage(
         "[Meter::RegisterMetricStorage] - Error during finding matching views."
         << "Some of the matching view configurations mayn't be used for metric collection");
   }
-  return std::move(storages);
+  return storages;
 }
 
 /** collect metrics across all the meters **/

sdk/test/metrics/attributes_hashmap_benchmark.cc

@@ -27,13 +27,12 @@ void BM_AttributseHashMap(benchmark::State &state)
 
   std::function<std::unique_ptr<Aggregation>()> create_default_aggregation =
       []() -> std::unique_ptr<Aggregation> {
-    auto agg = std::unique_ptr<Aggregation>(new DropAggregation);
-    return std::move(agg);
+    return std::unique_ptr<Aggregation>(new DropAggregation);
   };
 
   while (state.KeepRunning())
   {
-    for (int i = 0; i < MAX_THREADS; i++)
+    for (size_t i = 0; i < MAX_THREADS; i++)
     {
       workers.push_back(std::thread([&]() {
         hash_map.GetOrSetDefault(attributes[i % 2], create_default_aggregation)->Aggregate(1l);

sdk/test/metrics/attributes_hashmap_test.cc

@@ -49,8 +49,7 @@ TEST(AttributesHashMap, BasicTests)
   // GetOrSetDefault
   std::function<std::unique_ptr<Aggregation>()> create_default_aggregation =
       []() -> std::unique_ptr<Aggregation> {
-    auto agg = std::unique_ptr<Aggregation>(new DropAggregation);
-    return std::move(agg);
+    return std::unique_ptr<Aggregation>(new DropAggregation);
   };
   MetricAttributes m4 = {{"k1", "v1"}, {"k2", "v2"}, {"k3", "v3"}};
   EXPECT_NO_THROW(hash_map.GetOrSetDefault(m4, create_default_aggregation)->Aggregate(1l));