VS 2017程序无法识别“ scoped_lock” [英] VS 2017 program not recognizing "scoped_lock"

问题描述

我在VS 2017中使用scoped_locked时遇到了问题。我相信我可以追溯到< mutex> 声明，该声明复制如下。什么是最开始禁用 #if 开关以使用scoped_lock的最安全方法？再次感谢。

I've been having issues using scoped_locked in VS 2017. I believe I traced them back to the <mutex> declaration, copied below. What would be the safest way to disable the #if switch at the beginning to gain use to scoped_lock? Thanks again.

#if _HAS_CXX17
// CLASS TEMPLATE scoped_lock
template<class... _Mutexes>
class scoped_lock
{   // class with destructor that unlocks mutexes
public:
    explicit scoped_lock(_Mutexes&... _Mtxes)
    : _MyMutexes(_Mtxes...)
    {   // construct and lock
    _STD lock(_Mtxes...);
    }

    explicit scoped_lock(adopt_lock_t, _Mutexes&... _Mtxes)
    : _MyMutexes(_Mtxes...)
    {   // construct but don't lock
    }

    ~scoped_lock() _NOEXCEPT
    {   // unlock all
    _For_each_tuple_element(
        _MyMutexes,
        [](auto& _Mutex) _NOEXCEPT { _Mutex.unlock(); });
    }

    scoped_lock(const scoped_lock&) = delete;
    scoped_lock& operator=(const scoped_lock&) = delete;
private:
    tuple<_Mutexes&...> _MyMutexes;
};

推荐答案

从您的问题中不清楚您是否想要禁用/启用此行为。但通常可以使用 / std：c ++ latest 编译器参数和/或覆盖 _HAS_CXX17 来控制它 Visual C ++团队博客。问题在于，没有ovverides时， _HAS_CXX17 的定义取决于 yvals.h 中的编译器版本（请参见这个问题），因此这可能会因Visual Studio的版本而异（所以我可以不会给您一个直接的答案，因为尚不清楚您是否要禁用/启用它，以及确切的Visual Studio版本是什么，哪种组合将为您提供所需的结果。如文章中所述，这样做的缺点是您可能会放弃其他功能，因为它们未提供对STL的精细控制。但是您可以尝试查看恢复为旧的STL行为是否会给您造成问题。

From your question it is not clear if you want to disable/enable this behavior. But in general this can be controlled with the /std:c++latest compiler argument and/or overriding _HAS_CXX17 as stated in the Visual C++ Team Blog. The issue is that without ovverides the _HAS_CXX17 is defined depending on the compiler version in yvals.h (see this question) and thus this may vary depending on the version of Visual Studio (so I can't give you a straighforward answer what combo will give you the needed result since it is not clear whether you want to disable/enable it, and what is your exact Visual Studio version). As mentioned in the article, this has the downside that you may loose other features, since they did not provide a fine grained control over the STL. But you can try and see if reverting to the old STL behavior causes issues for you.

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