C++ async return value different when using x64

问题

The following Code compiles using both Debug\Win32 and Debug \ x64 settings in VC2013, but when I use Debug \ x64 i get the following IntelliSense Error:

    IntelliSense: no operator "=" matches these operands
    operand types are: std::future<bar<int>> = std::future<bar<int> (&)(bar<int> v)>

The Error refers to this function in Header.cpp:

bar<int> test::call(bar<int> v)
{
    std::future<bar<int>> ret;
    ret = std::async(std::launch::async, &test::exec, this, v);

    return ret.get();
}

Why does std::async return something diffrent when using x64?

return value win32:

std::future<bar<int>>

return value x64:

std::future<bar<int> (&)(bar<int>

How can i fix this for x64?

My Code:

Header.h

#pragma once
#include <future>
#include <iostream>

using namespace std;

template <typename T>
class bar
{
public:
    bar()
    {
        state = 9;
    }

    void dec(){ state--; }

    T show()
    {
        return state;
    }

private:
    T state;
};



class test{
public:
    test(int a);

public:
    bar<int> call(bar<int> v);

private:
    bar<int> exec(bar<int> v);




private:
    int value;
};

Header.cpp

#include "Header.h"


using namespace std;


test::test(int a)
{
    value = a;
}

bar<int> test::call(bar<int> v)
{
    std::future<bar<int>> ret;
    ret = std::async(std::launch::async, &test::exec, this, v);

    return ret.get();
}

bar<int> test::exec(bar<int> v)
{
    v.dec();
    v.dec();
    return v;
}

Source.cpp

#include <future>
#include <iostream>

#include "Header.h"

using namespace std;   

int main()
{
    test object(4);
    bar<int> foo;
    bar<int> other = object.call(foo);
    std::cout << other.show();
    getchar();
}

Edit: I do not want to use auto, because auto would not work in other scenarios (for example creating a vector of futures and then pushing back futures)

This Error is NOT a compiler error, the code compiles and executes flawlesly ==> i can't post the compiler error because there is no compiler error. I just want to get rid of the VC IntelliSense Error

Using std::move() does not solve the problem, i still get an IntelliSense Error: (The Code compiles and executes perfectly with and without the use of std::move)

IntelliSense: no operator "=" matches these operands
            operand types are: std::future<bar<int>> = std::future<bar<int> (&)(bar<int> v)>

来源：https://stackoverflow.com/questions/27652485/c-async-return-value-different-when-using-x64

标签

c++

visual-studio

visual-studio-2013

64-bit

stdasync