C ++ 11 future_status :: deferred无法正常工作 [英] C++ 11 future_status::deferred not working

问题描述

#include <iostream>
#include <future>
#include <chrono>

using namespace std;
using namespace std::chrono;

int sampleFunction(int a)
{
    return a;
}

int main()
{
   future<int> f1=async(launch::deferred,sampleFunction,10);
   future_status statusF1=f1.wait_for(seconds(10));
   if(statusF1==future_status::ready)
        cout<<"Future is ready"<<endl;
   else if (statusF1==future_status::timeout)
        cout<<"Timeout occurred"<<endl;
   else if (statusF1==future_status::deferred)
        cout<<"Task is deferred"<<endl;
   cout<<"Value : "<<f1.get()<<endl;
}

Output -
Timeout occurred
Value : 10

在上面的示例中，我期望future_status是deferred而不是timeout. sampleFunction已作为launch::deferred启动.因此，只有在调用f1.get()之前，它才会执行.在这种情况下，wait_for应该返回了future_status::deferred而不是future_status::timeout.

In above example, I was expecting future_status to be deferred instead of timeout. sampleFunction has been launched as launch::deferred. Hence it will not be executed until f1.get() has been called. In such condition wait_for should have returned future_status::deferred and not future_status::timeout.

感谢有人可以帮助我理解这一点. 我在fedora 17上使用的是g ++版本4.7.0.

Appreciate if someone can help me understand this. I am using g++ version 4.7.0 on fedora 17.

推荐答案

GCC和GNU STL不支持完整的C ++11.

GCC and the GNU STL have no support of the complete C++ 11.

您可以在此处查看GCC和GNU STL中C ++ 11的实现状态:

Here you can check out the C++ 11 implementation status in GCC and GNU STL:

http://gcc.gnu.org/projects/cxx0x.html

http://gcc.gnu.org/onlinedocs/libstdc++/manual/status.html

此外，请阅读此讨论主题: http://blog.gmane .org/gmane.comp.gcc.bugs/month = 20120201

Also, read this discussion thread: http://blog.gmane.org/gmane.comp.gcc.bugs/month=20120201

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