More code changes to prevent use-after-free

Author: bajajneha27

google/cloud/storage/internal/bucket_metadata_cache.h

@@ -19,6 +19,7 @@
 #include "absl/types/optional.h"
 #include <cstddef>
 #include <list>
+#include <memory>
 #include <mutex>
 #include <string>
 #include <unordered_map>
@@ -68,15 +69,23 @@ class BucketMetadataCache {
 
 class ScopedFetch {
  public:
-  ScopedFetch(BucketMetadataCache* cache, std::string bucket_name)
-      : cache_(cache), bucket_name_(std::move(bucket_name)) {}
-  ~ScopedFetch() {
-    if (cache_) cache_->EndFetch(bucket_name_);
-  }
+  ScopedFetch() = default;
+  ScopedFetch(std::shared_ptr<BucketMetadataCache> cache,
+              std::string bucket_name)
+      : state_(std::make_shared<State>(std::move(cache),
+                                       std::move(bucket_name))) {}
 
  private:
-  BucketMetadataCache* cache_;
-  std::string bucket_name_;
+  struct State {
+    State(std::shared_ptr<BucketMetadataCache> c, std::string b)
+        : cache(std::move(c)), bucket_name(std::move(b)) {}
+    ~State() {
+      if (cache) cache->EndFetch(bucket_name);
+    }
+    std::shared_ptr<BucketMetadataCache> cache;
+    std::string bucket_name;
+  };
+  std::shared_ptr<State> state_;
 };
 
 GOOGLE_CLOUD_CPP_INLINE_NAMESPACE_END

google/cloud/storage/internal/tracing_connection.cc

@@ -31,8 +31,8 @@ GOOGLE_CLOUD_CPP_INLINE_NAMESPACE_BEGIN
 TracingConnection::TracingConnection(std::shared_ptr<StorageConnection> impl,
                                      AsyncRunner runner)
     : impl_(std::move(impl)),
-      runner_(std::move(runner)),
-      cache_(std::make_shared<BucketMetadataCache>(10000)) {}
+      cache_(std::make_shared<BucketMetadataCache>()),
+      runner_(std::move(runner)) {}
 
 TracingConnection::~TracingConnection() = default;
 
@@ -53,8 +53,6 @@ TracingConnection::AsyncRunner const& TracingConnection::runner() {
 
 BucketMetadataCache& TracingConnection::cache() const { return *cache_; }
 
-void TracingConnection::ResetCacheForTesting() { cache().Clear(); }
-
 Options TracingConnection::options() const { return impl_->options(); }
 
 void TracingConnection::EnrichSpan(opentelemetry::trace::Span& span,
@@ -69,10 +67,10 @@ void TracingConnection::MaybeTriggerBackgroundFetch(
     return;
   }
 
+  auto guard = ScopedFetch(cache_, bucket_name);
   auto current_options = google::cloud::internal::SaveCurrentOptions();
-  runner()([impl = impl_, cache = cache_, bucket_name, current_options]() {
-    ScopedFetch guard(cache.get(), bucket_name);
-
+  runner()([impl = impl_, cache = cache_, bucket_name, current_options,
+            guard]() {
     google::cloud::internal::OptionsSpan span(current_options);
     storage::internal::GetBucketMetadataRequest request(bucket_name);
     auto result = impl->GetBucketMetadata(request);

google/cloud/storage/internal/tracing_connection.h

@@ -36,8 +36,6 @@ class TracingConnection : public storage::internal::StorageConnection {
                              AsyncRunner runner = {});
   ~TracingConnection() override;
 
-  void ResetCacheForTesting();
-
   Options options() const override;
 
   StatusOr<storage::internal::ListBucketsResponse> ListBuckets(
@@ -209,9 +207,9 @@ class TracingConnection : public storage::internal::StorageConnection {
   AsyncRunner const& runner();
 
   std::shared_ptr<StorageConnection> impl_;
-  AsyncRunner runner_;
   std::shared_ptr<BucketMetadataCache> cache_;
   absl::once_flag once_flag_;
+  AsyncRunner runner_;
 };
 
 std::shared_ptr<storage::internal::StorageConnection> MakeTracingClient(