Question

我使用nbind - GitHub link编写C ++插件用于大多数事情，Nan - GitHub link用于调用异步调用。当我只调用一次回调时，它完美无缺。但是当我两次调用回调时，它会给出Segmentation fault (core dumped)。使用gdb无法发现错误。这是JS和C ++代码（使用node-gyp configure build进行编译）：

//main.js code
var nbind = require('nbind');
var lib = nbind.init().lib;

lib.HeaderExample.callJS(function(a) {
console.log("result" + a);
});

lib.HeaderExample.startThread();
lib.HeaderExample.startThread();

C ++插件的代码

//c++ code
class CallbackRunner : public Nan::AsyncWorker {
public:
    CallbackRunner(Nan::Callback *callback)
            : AsyncWorker(callback) {}
    void Execute () {}
    void HandleOKCallback () {
        std::cout << "running HandleOKCallback in thread " << std::this_thread::get_id() << std::endl;
        Nan::HandleScope scope;
        v8::Local<v8::Value> argv[] = {
                Nan::New<v8::Number>(10)
        };
        callback->Call(1, argv);
    }
};

class HeaderExample {
public:
    static void callJS(nbind::cbFunction &callback) {
        std::cout << "running callJS in thread " << std::this_thread::get_id() << std::endl;
        m_onInitialisationStarted = new nbind::cbFunction(callback);
        Nan::Callback *callbackNan = new Nan::Callback(m_onInitialisationStarted->getJsFunction());
        runner = new CallbackRunner(callbackNan);
    }
    static void startThread() {
        std::cout << "it is here";
        std::thread threadS(some);
        threadS.join();
    }
    static void some() {
        std::cout << "running some in thread: " << std::this_thread::get_id() << std::endl;
        if(runner){
        AsyncQueueWorker(runner);
        }
    }
    inline static nbind::cbFunction *m_onInitialisationStarted = 0;
    inline static CallbackRunner *runner;
};

Answer 1

您不能让两个线程同时调用同一个V8实例。您需要小心锁定以确保在任何时间点只有一个线程与V8交互。

Answer 2

在回调完成后，您的班级会使用AsyncQueueWorker来调用CallbackRunner，但AsyncQueueWorker来电AsyncExecuteComplete，然后调用worker->Destroy()。请参阅AsyncQueueWorker中的nan.h代码：

inline void AsyncExecute (uv_work_t* req) {
  AsyncWorker *worker = static_cast<AsyncWorker*>(req->data);
  worker->Execute();
}

inline void AsyncExecuteComplete (uv_work_t* req) {
  AsyncWorker* worker = static_cast<AsyncWorker*>(req->data);
  worker->WorkComplete();
  worker->Destroy();
}

inline void AsyncQueueWorker (AsyncWorker* worker) {
  uv_queue_work(
      uv_default_loop()
    , &worker->request
    , AsyncExecute
    , reinterpret_cast<uv_after_work_cb>(AsyncExecuteComplete)
  );
}

worker->Destroy()将删除CallbackRunner类以及您提供给其构造函数的Nan::Callback。这就是为什么在尝试第二次调用此回调时出现分段错误的原因。

您可能最好以Nan::AsyncProgressQueueWorker代替Nan::AsyncWorker开课。 AsyncProgressQueueWorker继承AsyncWorker，它允许您像AsyncWorker一样从主线程安排工作，但它为您提供了一个ExecutionProgress类，允许您使用任何线程在原始预定作业运行时，多次回调主线程。

Nan::AsyncProgressQueueWorker已添加到版本2.8.0中的 NAN

两次调用一些回调函数会导致分段错误：Nan

2 个答案: