C ++临时变量生命周期 [英] C++ temporary variable lifetime

问题描述

此代码是否有效？

int foo()
{
    std::vector<std::string>& v = std::vector<std::string>(5, "X");

    // Do something silly...

    return 42;
}

由于某种原因，我认为临时 std： ： 应该在构造之后立即被破坏（因此使引用无效）。

For some reason I thought that the temporary std::vector object (right from the assignment sign) should be destructed right after it's construction (thus rendering the reference invalid).

但是，调试证明我错了，我意识到我不太明白为什么临时变量在函数返回时被破坏。 strong>

However, debugging proves that I'm wrong and, well, I realized that I don't quite understand why does the temporary variable is destructed when the function returns.

我想我对某些基本要素有很强的误解，所以请赐教： em>

I guess I have a strong misunderstanding of something fundamental, so please enlighten me :)

推荐答案

您显示的代码是非法的–临时只能绑定到右值引用或 const 左值引用。

The code you've shown is illegal – temporaries can only bind to rvalue references or const lvalue references.

VC ++恰好允许它作为一个扩展http://msdn.microsoft.com/en-us/library/186yxbac.aspx\"> a level 4 warning that so）。

VC++ happens to allow it as an extension (and gives a level 4 warning saying so).

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