Memory leak in Native Modules with RCT_EXPORT_METHOD

[nikolaytsigvintsev]

Hi !

Problem:
Memory leak and application crash on RCT_EXPORT_METHOD

When developing a module, I ran into a memory leak problem in NativeModules.
A memory leak occurs when the resolve() function is called from the Objective-C module with data transfer to the JS function.

React Native version:
System:
OS: macOS Mojave 10.14.5
CPU: (8) x64 Intel(R) Core(TM) i7-7820HQ CPU @ 2.90GHz
Memory: 421.92 MB / 16.00 GB
Shell: 3.2.57 - /bin/bash
Binaries:
Node: 12.12.0 - /usr/local/bin/node
Yarn: 1.19.1 - /usr/local/bin/yarn
npm: 6.11.3 - /usr/local/bin/npm
Watchman: 4.9.0 - /usr/local/bin/watchman
SDKs:
iOS SDK:
Platforms: iOS 13.0, DriverKit 19.0, macOS 10.15, tvOS 13.0, watchOS 6.0
IDEs:
Xcode: 11.0/11A420a - /usr/bin/xcodebuild
npmPackages:
react: 16.9.0 => 16.9.0
react-native: 0.61.2 => 0.61.2
npmGlobalPackages:
react-native-cli: 2.0.1
iPad: 12.1

Steps To Reproduce

I wrote a test code:

FileReader.h

#ifndef FileReader_h
#define FileReader_h

#import <React/RCTBridgeModule.h>

@interface FileReader : NSObject <RCTBridgeModule>
@end

#endif /* FileReader_h */

FileReader.m

#import <Foundation/Foundation.h>
#import “FileReader.h”
#import <React/RCTLog.h>

@implementation FileReader

RCT_EXPORT_MODULE();

RCT_EXPORT_METHOD(read:(NSString *)read
                  resolver:(RCTPromiseResolveBlock)resolve
                  rejecter:(RCTPromiseRejectBlock)reject)
{
  NSLog(@"JS: start");
  @autoreleasepool {    
      NSMutableString *nameString = [[NSMutableString alloc] init];
      for (int i = 1; i <= 3000000; i++)
      {
       [nameString appendString:@"1234567890"];
      }
      NSLog(@"JS: send string");
    
    resolve(nameString);
  }
}
@end

FileReader.js

……..
import {NativeModules} from 'react-native';

const FileReader = NativeModules.FileReader;

const onRead= async () => {
  for (let i = 0; i < 1000; i++) {
    await FileReader.read('Start').then(response => {
        console.log('Step: ', i);
    });
  }
};
…….

Describe what you expected to happen:
I wish the memory leak disappeared

Videoreport:
https://www.dropbox.com/s/aq9nu44tcziqulb/Screen%20Recording%202019-10-23%20at%2017.06.14.mov?dl=0

Thanks!

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