Fix potential memory leak in Family

Author: jerryct

core/include/prometheus/detail/future_std.h

@@ -0,0 +1,16 @@
+#pragma once
+
+#include <memory>
+#include <utility>
+
+namespace prometheus {
+namespace detail {
+
+// Remove as soon C++14 can be used.
+template <typename T, typename... Args>
+std::unique_ptr<T> make_unique(Args&&... args) {
+  return std::unique_ptr<T>(new T(std::forward<Args>(args)...));
+}
+
+}  // namespace detail
+}  // namespace prometheus

core/include/prometheus/family.h

@@ -15,6 +15,7 @@
 #include "prometheus/check_names.h"
 #include "prometheus/client_metric.h"
 #include "prometheus/collectable.h"
+#include "prometheus/detail/future_std.h"
 #include "prometheus/metric_family.h"
 
 namespace prometheus {
@@ -162,11 +163,12 @@ T& Family<T>::Add(const std::map<std::string, std::string>& labels,
 #endif
     return *metrics_iter->second;
   } else {
-    auto metric = new T(std::forward<Args>(args)...);
-    metrics_.insert(std::make_pair(hash, std::unique_ptr<T>{metric}));
+    auto metric =
+        metrics_.insert(std::make_pair(hash, detail::make_unique<T>(args...)));
+    assert(metric.second);
     labels_.insert({hash, labels});
-    labels_reverse_lookup_.insert({metric, hash});
-    return *metric;
+    labels_reverse_lookup_.insert({metric.first->second.get(), hash});
+    return *(metric.first->second);
   }
 }
 

core/tests/family_test.cc

@@ -5,6 +5,7 @@
 #include <gmock/gmock.h>
 
 #include "prometheus/client_metric.h"
+#include "prometheus/detail/future_std.h"
 #include "prometheus/histogram.h"
 
 namespace prometheus {
@@ -65,7 +66,8 @@ TEST(FamilyTest, add_twice) {
 
 TEST(FamilyTest, should_assert_on_invalid_metric_name) {
   auto create_family_with_invalid_name = []() {
-    return new Family<Counter>("", "empty name", {});
+    return detail::make_unique<Family<Counter>>(
+        "", "empty name", std::map<std::string, std::string>{});
   };
   EXPECT_DEBUG_DEATH(create_family_with_invalid_name(),
                      ".*Assertion `CheckMetricName.*");