Memory leak on macOS when use C++ std::thread

[tianlei124]

I used std::thread in the C++ addon code, and a memory leak is found using LeakTracer.
Here is my C++ addon code:

#include <node_api.h>

#include "leaktracer.h"

namespace demo {

napi_value Method(napi_env env, napi_callback_info args) {
  napi_value greeting;
  napi_status status;
  leaktracer_startMonitoringAllThreads();
  {
      auto t = std::thread([]{ printf("hello"); });
      t.join();
  }
  // std::this_thread::sleep_for(std::chrono::seconds(3));
  status = napi_create_string_utf8(env, "world", NAPI_AUTO_LENGTH, &greeting);
  if (status != napi_ok) return nullptr;
  leaktracer_stopAllMonitoring();
  leaktracer_writeLeaksToFile("./leaks.txt");

  return greeting;
}

napi_value init(napi_env env, napi_value exports) {
  napi_status status;
  napi_value fn;

  status = napi_create_function(env, nullptr, 0, Method, nullptr, &fn);
  if (status != napi_ok) return nullptr;

  status = napi_set_named_property(env, exports, "hello", fn);
  if (status != napi_ok) return nullptr;
  return exports;
}

NAPI_MODULE(NODE_GYP_MODULE_NAME, init)

}  // namespace demo

Then js code which invoke addon:

// hello.js
const addon = require('./build/Debug/addon');
console.log(addon.hello());
// Prints: 'world'

The backtrace of leak is :
leaktracer::MemoryTrace::registerAllocation(void*, unsigned long, bool);operator new(unsigned long);std::__1::thread::thread<demo::Method(napi_env__*, napi_callback_info__*)::$_0, void>(demo::Method(napi_env__*, napi_callback_info__*)::$_0&&);std::__1::thread::thread<demo::Method(napi_env__*, napi_callback_info__*)::$_0, void>(demo::Method(napi_env__*, napi_callback_info__*)::$_0&&);demo::Method(napi_env__*, napi_callback_info__*);(anonymous namespace)::v8impl::FunctionCallbackWrapper::Invoke(v8::FunctionCallbackInfo<v8::Value> const&);v8::internal::FunctionCallbackArguments::Call(v8::internal::CallHandlerInfo*);v8::internal::MaybeHandle<v8::internal::Object> v8::internal::(anonymous namespace)::HandleApiCallHelper<false>(v8::internal::Isolate*, v8::internal::Handle<v8::internal::HeapObject>, v8::internal::Handle<v8::internal::HeapObject>, v8::internal::Handle<v8;v8::internal::Builtin_Impl_HandleApiCall(v8::internal::BuiltinArguments, v8::internal::Isolate*)

I have tested on Windows10, Debian9, macOS10.15(Intel CPU) macOS11.3(M1), only macOS has leak.
Does anyone know why this is?

[mhdawson]

Vladimir mentioned that he has seen something like this as newer thread implementations use pooling so that when the thread completes it is not necessary released.

You could try starting/stopping many threads (say 1000 times) and validate that after some number it does not show additional leaks.

We don't think this is related to node-addon-api at all, the same could outside an addon should report the same thing.

[vmoroz]

Please see the related discussion on the Android NDK: android/ndk#819

[tianlei124]

Thanks a lot, I understand.