From 53782eafc96d9f0564e25c668c57a60321ccc2ec Mon Sep 17 00:00:00 2001
From: Valentin Shergin <shergin@fb.com>
Date: Sun, 25 Mar 2018 22:43:26 -0700
Subject: [PATCH] Fabric: Source shadow node is now stored as a weak pointer

Summary:
We use shource nodes only in the diffing alogorithm. It implies that we have strong pointers to those nodes in trees we compare against.
Using weak_ptr's allows to avoid memory leaks.

Reviewed By: mdvacca

Differential Revision: D7376348

fbshipit-source-id: 34e5f58f18a00475f6bcdfbea3996b41c84dff62
---
 ReactCommon/fabric/core/shadownode/ShadowNode.cpp | 9 +++++----
 ReactCommon/fabric/core/shadownode/ShadowNode.h   | 3 ++-
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/ReactCommon/fabric/core/shadownode/ShadowNode.cpp b/ReactCommon/fabric/core/shadownode/ShadowNode.cpp
index 04fb5d30f..e1394cccc 100644
--- a/ReactCommon/fabric/core/shadownode/ShadowNode.cpp
+++ b/ReactCommon/fabric/core/shadownode/ShadowNode.cpp
@@ -68,7 +68,7 @@ InstanceHandle ShadowNode::getInstanceHandle() const {
 }
 
 SharedShadowNode ShadowNode::getSourceNode() const {
-  return sourceNode_;
+  return sourceNode_.lock();
 }
 
 void ShadowNode::sealRecursive() const {
@@ -111,7 +111,7 @@ void ShadowNode::replaceChild(const SharedShadowNode &oldChild, const SharedShad
 
 void ShadowNode::clearSourceNode() {
   ensureUnsealed();
-  sourceNode_ = nullptr;
+  sourceNode_.reset();
 }
 
 #pragma mark - DebugStringConvertible
@@ -146,10 +146,11 @@ SharedDebugStringConvertibleList ShadowNode::getDebugProps() const {
     list.push_back(std::make_shared<DebugStringConvertibleItem>("handle", std::to_string((size_t)instanceHandle_)));
   }
 
-  if (sourceNode_) {
+  SharedShadowNode sourceNode = getSourceNode();
+  if (sourceNode) {
     list.push_back(std::make_shared<DebugStringConvertibleItem>(
       "source",
-      sourceNode_->getDebugDescription({.maximumDepth = 1, .format = false})
+      sourceNode->getDebugDescription({.maximumDepth = 1, .format = false})
     ));
   }
 
diff --git a/ReactCommon/fabric/core/shadownode/ShadowNode.h b/ReactCommon/fabric/core/shadownode/ShadowNode.h
index 1deb4d520..aa68556f9 100644
--- a/ReactCommon/fabric/core/shadownode/ShadowNode.h
+++ b/ReactCommon/fabric/core/shadownode/ShadowNode.h
@@ -24,6 +24,7 @@ using SharedShadowNode = std::shared_ptr<const ShadowNode>;
 using SharedShadowNodeList = std::vector<std::shared_ptr<const ShadowNode>>;
 using SharedShadowNodeSharedList = std::shared_ptr<const SharedShadowNodeList>;
 using SharedShadowNodeUnsharedList = std::shared_ptr<SharedShadowNodeList>;
+using WeakShadowNode = std::weak_ptr<const ShadowNode>;
 
 class ShadowNode:
   public virtual Sealable,
@@ -79,7 +80,7 @@ protected:
   InstanceHandle instanceHandle_;
   SharedProps props_;
   SharedShadowNodeSharedList children_;
-  SharedShadowNode sourceNode_;
+  WeakShadowNode sourceNode_;
 };
 
 } // namespace react