c + +可以通过引用传递临时的lambda(在msvc/windows上有效，但在gcc/linux上无效)吗? [英] c++ can a temporary lambda be passed by reference (works on msvc/windows but not gcc/linux)?

问题描述

可以说我有以下代码片段:

Lets say I have the following code snippets:

// global variable
std::thread worker_thread;

// Template function
template <typename Functor>
void start_work(Functor &worker_fn)  // lambda passed by ref
{
    worker_thread = std::thread([&](){
        worker_fn();
    });
}

这样称呼:

void do_work(int value)
{
    printf("Hello from worker\r\n");
}

int main()
{
    // This lambda is a temporary variable...
    start_work([do_work](int value){ do_work(value) });
}

我开始在MSVC2012上进行开发.所有这些都整理得很好，并且似乎可以正常工作.但是，当我转移到Linux平台上的gcc编译器时，出现以下(缩写)错误:

I started developing on MSVC2012. This all compiled up fine and seemed to work. However when I moved onto the gcc compiler on Linux platform I got the following (abbreviated) error:

no known conversion for argument 1 '...__lambda3' to '...__lambda3&'

我的问题:

• 因此，从错误中我认为lambda是一个临时变量，因此不能通过引用传递-是吗?
• 也-您知道为什么它可以与MSVC一起使用吗? -可以自动修复我写的内容吗?

推荐答案

MSVC不同于标准，它允许匿名临时对象绑定到非常量左值引用.您可以使用/Za编译器标志(禁用语言扩展")或MSVC2017中更清晰的/permissive-选项将其关闭.

MSVC deviates from the standard in that it allows anonymous temporaries to be bound to non-const lvalue references. You can switch this off using the /Za compiler flag ("disable language extensions"), or the sharper /permissive- option from MSVC2017.

C ++标准一直很明确，匿名临时对象只能绑定到const引用.

The C++ standard has always been clear that anonymous temporaries can only bind to const references.

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