这个 `context_.Reset` 在 react-native js-runtime 的 v8 运行时实现中做了什么？

Question

我是 c++ 和 v8 引擎的菜鸟。当我查看 v8 JSI 实现的源代码时，我发现我无法理解：这是 v8 运行时的构造函数：（请参阅下面的注释行）

V8Runtime::V8Runtime(const std::string &timezoneId) {
  if (!s_platform) {
    s_platform = v8::platform::NewDefaultPlatform();
    v8::V8::InitializeICU();
    v8::V8::InitializePlatform(s_platform.get());
    v8::V8::Initialize();
  }

  arrayBufferAllocator_.reset(
      v8::ArrayBuffer::Allocator::NewDefaultAllocator());
  v8::Isolate::CreateParams createParams;
  createParams.array_buffer_allocator = arrayBufferAllocator_.get();
  isolate_ = v8::Isolate::New(createParams);
#if defined(__ANDROID__)
  if (!timezoneId.empty()) {
    isolate_->DateTimeConfigurationChangeNotification(
        v8::Isolate::TimeZoneDetection::kCustom, timezoneId.c_str());
  }
#endif
  isolate_->Enter();
  v8::HandleScope scopedIsolate(isolate_);
  context_.Reset(isolate_, CreateGlobalContext(isolate_)); 
//what does this reset for? why I need to reset the context just after I create the global context of it?
  context_.Get(isolate_)->Enter();
}

下面是CreateGlobalContext的代码：

v8::Local<v8::Context> V8Runtime::CreateGlobalContext(v8::Isolate *isolate) {
  v8::HandleScope scopedIsolate(isolate);
  v8::Local<v8::ObjectTemplate> global = v8::ObjectTemplate::New(isolate_);
  global->Set(
      v8::String::NewFromUtf8(isolate, "_v8runtime", v8::NewStringType::kNormal)
          .ToLocalChecked(),
      v8::FunctionTemplate::New(isolate, V8Runtime::GetRuntimeInfo));
  return v8::Context::New(isolate_, nullptr, global);
}

repo 的来源是 here，一个 react-native js-runtime 的 v8 实现。提前致谢！

Answer 1

context_ 是一个全局句柄 (v8::Global)，它的 Reset(...) 方法是你如何分配给它包装的指针。因此，它正在从未初始化状态“重置”为在此处存储新创建的全局上下文。

This is probably just defensive programming. – Botje

不，防御性编程与它无关。

Just treat it as an assignment. – Botje

是的。如果 context_ 是 v8::Local（由于其他原因这会成为问题），那么您只会在此处看到 context_ = CreateGlobalContext(...)。

这个 `context_.Reset` 在 react-native js-runtime 的 v8 运行时实现中做了什么？

what does this `context_.Reset` do in v8 runtime implemation of react-native js-runtime?

c++

v8

react-native