无法通过“回调"访问V8上下文功能 [英] Can't access V8 Context in "callback" function

问题描述

我正在编写一个NodeJS插件，其中使用了一个C库，该库可让您在某些事件下注册回调.触发回调后，我想调用NodeJS回调函数.问题是，在我的C回调函数中，尝试执行与V8相关的任何操作(例如创建HandleScope)时都会遇到分段错误.

I am writing a NodeJS addon where I use a C library that lets you register a callback at certain events. When the callback is fired I want to call a NodeJS callback function. The problem is that in my C callback function I get a segmentation fault when trying to do anything V8 related, like creating a HandleScope.

在test.js中:

...

myaddon.register(function(data) {
  console.log("data: " + JSON.stringify(data));
});

...

在test.c中:

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <node.h>
#include <v8.h>

using namespace v8;

void WINAPI myEvent(int num, void * context) {
  HandleScope scope; // Segmentation fault here!

  Local<Function> * cb = (Local<Function>*)(context);

  Local<Object> obj = Object::New();
  obj->Set(String::NewSymbol("id"), Number::New(num));

  const int argc = 1;
  Local<Value> argv[argc] = { obj };
  (*cb)->Call(Context::GetCurrent()->Global(), argc, argv);

  sleep(1);
}

Handle<Value> RegisterEvent(const Arguments& args) {
    HandleScope scope;

    Local<Function> cb = Local<Function>::Cast(args[0]);

    int callbackId  = registerEvent((Event)&myEvent, &cb );
    printf("callback id: %i\n", callbackId);

    init();

    return scope.Close(Integer::New(callbackId));
}

void init(Handle<Object> exports) {
  exports->Set(String::NewSymbol("register"),
      FunctionTemplate::New(RegisterEvent)->GetFunction());
}

NODE_MODULE(test, init)

已更新为真实代码.

我刚刚更改了此问题的标题，因为问题可能是我的回调函数无法访问V8上下文.由于在创建HandleScope实例时遇到分段错误，因此看不到其他问题.除了这个问题之外，我正在尝试在V8文档中找到答案，但这非常庞大，而且我没有太多时间来测试和研究.

I just changed the title of this issue since the problem is probably that my callback function can't access the V8 Context. Since I get a segmentation fault when creating HandleScope instance I can't see what else it might be. In addition to this question I AM trying to find the answer in the V8 documentation, but it is huge and I don't have that much time to test and investigate.

推荐答案

必须在V8线程中调用处理程序函数myEvent().如果没有，则必须将事件通知发布到V8线程中:

Your handler function myEvent() must be called in V8 thread. If not, you have to post the event notification into the V8 thread:

https://stackoverflow.com/a/15701160/1355844

https://stackoverflow.com/a/22946062/1355844

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