From 9b76e217bb16935069f0ea5b60f4c4d9b73f86d6 Mon Sep 17 00:00:00 2001
From: Ramanpreet Nara <ramanpreet@fb.com>
Date: Thu, 17 Sep 2020 13:52:44 -0700
Subject: [PATCH] Copy all blocks generated by TurboModules
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Summary:
The Apple documentation states: https://developer.apple.com/library/archive/documentation/Cocoa/Conceptual/Blocks/Articles/bxUsing.html#//apple_ref/doc/uid/TP40007502-CH5-SW1

> Typically, you shouldn’t need to copy (or retain) a block. You only need to make a copy when you expect the block to be used after destruction of the scope within which it was declared. Copying moves a block to the heap.

All blocks generated in the TurboModule infra, for callbacks and promise resolve/reject handlers, can be used after the destruction of the scope within which they were declared. Therefore, let's copy them in the hopes that they mitigate T75876134.

**Note:** We copy blocks before pushing them into the `retainedObjects` array in the legacy Infra as well. Context: D2559997 (https://github.com/facebook/react-native/commit/71da2917e577b7ec659083408cff7f9981d6600f), D5589246 (https://github.com/facebook/react-native/commit/2a6965df9063c795b3d3098c4db76e5f595ba44f)

Changelog: [Internal]

Reviewed By: fkgozali

Differential Revision: D23764329

fbshipit-source-id: e71360977bdff74dc570bd40f0139792860f811f
---
 .../core/platform/ios/RCTTurboModule.mm       | 20 +++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/ReactCommon/turbomodule/core/platform/ios/RCTTurboModule.mm b/ReactCommon/turbomodule/core/platform/ios/RCTTurboModule.mm
index 4e5cdc8a4e..c8950c5718 100644
--- a/ReactCommon/turbomodule/core/platform/ios/RCTTurboModule.mm
+++ b/ReactCommon/turbomodule/core/platform/ios/RCTTurboModule.mm
@@ -171,7 +171,7 @@ convertJSIFunctionToCallback(jsi::Runtime &runtime, const jsi::Function &value,
 {
   auto weakWrapper = CallbackWrapper::createWeak(value.getFunction(runtime), runtime, jsInvoker);
   BOOL __block wrapperWasCalled = NO;
-  return ^(NSArray *responses) {
+  RCTResponseSenderBlock callback = ^(NSArray *responses) {
     if (wrapperWasCalled) {
       throw std::runtime_error("callback arg cannot be called more than once");
     }
@@ -194,6 +194,8 @@ convertJSIFunctionToCallback(jsi::Runtime &runtime, const jsi::Function &value,
 
     wrapperWasCalled = YES;
   };
+
+  return [callback copy];
 }
 
 namespace facebook {
@@ -331,12 +333,11 @@ jsi::Value ObjCTurboModule::performMethodInvocation(
   bool wasMethodSync = isMethodSync(returnType);
 
   void (^block)() = ^{
-    if (!weakModule) {
+    id<RCTTurboModule> strongModule = weakModule;
+    if (!strongModule) {
       return;
     }
 
-    id<RCTTurboModule> strongModule = weakModule;
-
     if (wasMethodSync) {
       TurboModulePerfLogger::syncMethodCallExecutionStart(moduleName, methodNameStr.c_str());
     } else {
@@ -635,10 +636,13 @@ jsi::Value ObjCTurboModule::invokeObjCMethod(
             runtime,
             jsInvoker_,
             ^(RCTPromiseResolveBlock resolveBlock, RCTPromiseRejectBlock rejectBlock) {
-              [inv setArgument:(void *)&resolveBlock atIndex:count + 2];
-              [inv setArgument:(void *)&rejectBlock atIndex:count + 3];
-              [retainedObjectsForInvocation addObject:resolveBlock];
-              [retainedObjectsForInvocation addObject:rejectBlock];
+              RCTPromiseResolveBlock resolveCopy = [resolveBlock copy];
+              RCTPromiseRejectBlock rejectCopy = [rejectBlock copy];
+
+              [inv setArgument:(void *)&resolveCopy atIndex:count + 2];
+              [inv setArgument:(void *)&rejectCopy atIndex:count + 3];
+              [retainedObjectsForInvocation addObject:resolveCopy];
+              [retainedObjectsForInvocation addObject:rejectCopy];
               // The return type becomes void in the ObjC side.
               performMethodInvocation(runtime, VoidKind, methodName, inv, retainedObjectsForInvocation);
             })