Fix leaks in Firestore (#2199)

* Clean up retain cycle in FSTLevelDB.

* Explicitly CFRelease our SCNetworkReachabilityRef.

* Make gRPC stream delegates weak

Author: wilhuff

Firestore/Source/Local/FSTLRUGarbageCollector.mm

@@ -81,7 +81,7 @@ size_t size() const {
 };
 
 @implementation FSTLRUGarbageCollector {
-  id<FSTLRUDelegate> _delegate;
+  __weak id<FSTLRUDelegate> _delegate;
   LruParams _params;
 }
 

Firestore/Source/Local/FSTLevelDBMutationQueue.mm

@@ -86,7 +86,8 @@ - (instancetype)initWithUserID:(std::string)userID
 @end
 
 @implementation FSTLevelDBMutationQueue {
-  FSTLevelDB *_db;
+  // This instance is owned by FSTLevelDB; avoid a retain cycle.
+  __weak FSTLevelDB *_db;
 
   /** The normalized userID (e.g. nil UID => @"" userID) used in our LevelDB keys. */
   std::string _userID;

Firestore/Source/Local/FSTLevelDBQueryCache.mm

@@ -62,7 +62,8 @@ @interface FSTLevelDBQueryCache ()
 @end
 
 @implementation FSTLevelDBQueryCache {
-  FSTLevelDB *_db;
+  // This instance is owned by FSTLevelDB; avoid a retain cycle.
+  __weak FSTLevelDB *_db;
 
   /**
    * The last received snapshot version. This is part of `metadata` but we store it separately to

Firestore/core/src/firebase/firestore/remote/connectivity_monitor_apple.mm

@@ -77,7 +77,13 @@ void OnReachabilityChangedCallback(SCNetworkReachabilityRef /*unused*/,
 class ConnectivityMonitorApple : public ConnectivityMonitor {
  public:
   explicit ConnectivityMonitorApple(AsyncQueue* worker_queue)
-      : ConnectivityMonitor{worker_queue}, reachability_{CreateReachability()} {
+      : ConnectivityMonitor{worker_queue} {
+    reachability_ = CreateReachability();
+    if (!reachability_) {
+      LOG_DEBUG("Failed to create reachability monitor.");
+      return;
+    }
+
     SCNetworkReachabilityFlags flags;
     if (SCNetworkReachabilityGetFlags(reachability_, &flags)) {
       SetInitialStatus(ToNetworkStatus(flags));
@@ -108,10 +114,14 @@ explicit ConnectivityMonitorApple(AsyncQueue* worker_queue)
   }
 
   ~ConnectivityMonitorApple() {
-    bool success =
-        SCNetworkReachabilitySetDispatchQueue(reachability_, nullptr);
-    if (!success) {
-      LOG_DEBUG("Couldn't unset reachability queue");
+    if (reachability_) {
+      bool success =
+          SCNetworkReachabilitySetDispatchQueue(reachability_, nullptr);
+      if (!success) {
+        LOG_DEBUG("Couldn't unset reachability queue");
+      }
+
+      CFRelease(reachability_);
     }
   }
 
@@ -121,7 +131,7 @@ void OnReachabilityChanged(SCNetworkReachabilityFlags flags) {
   }
 
  private:
-  SCNetworkReachabilityRef reachability_;
+  SCNetworkReachabilityRef reachability_ = nil;
 };
 
 namespace {

Firestore/core/src/firebase/firestore/remote/remote_objc_bridge.h

@@ -185,7 +185,7 @@ class WatchStreamDelegate {
   void NotifyDelegateOnClose(const util::Status& status);
 
  private:
-  id<FSTWatchStreamDelegate> delegate_;
+  __weak id<FSTWatchStreamDelegate> delegate_;
 };
 
 /** A C++ bridge that invokes methods on an `FSTWriteStreamDelegate`. */
@@ -202,7 +202,7 @@ class WriteStreamDelegate {
   void NotifyDelegateOnClose(const util::Status& status);
 
  private:
-  id<FSTWriteStreamDelegate> delegate_;
+  __weak id<FSTWriteStreamDelegate> delegate_;
 };
 
 }  // namespace bridge