什么是类数据成员的生命周期，const引用一个右值？ [英] What is the lifetime of the class data member which const reference to a rvalue?

问题描述

一般来说，此讨论仅限于本地函数变量：

Generally this discussion is up to the local function variable only:

void foo (const int &i)
{
  // use i till foo() ends
}
foo(3);

但是，此规则适用于 class member也？

But, does this rule applies to the class member also ?

struct A {
  const int &a;
  A () : a(3) {}  // version 1
  A (const int &i) : a(i) {} // version 2
};

现在 A 用作

{
  return ()? new A : new A(3) : new A(some_local_variable);
}

a 新分配的整个生命周期内 A

Will the contents of a remain same through out the life time of the all 3 newly allocated A ?

推荐答案

C ++ 03标准12.2 / 5临时对象部分）适当地回答了您的问题：

The C++03 standard (Section "12.2/5 Temporary objects") answers your question aptly:

引用绑定的临时文件或临时文件complete对象绑定到其临时绑定的子对象将持续参考的生命周期，除非下面指定。 在构造函数的ctor-initializer（12.6.2）中临时绑定到引用成员，直到构造函数退出。在函数调用（5.2.2）中，引用参数的临时绑定将持续到包含调用的完整表达式完成。

The temporary to which the reference is bound or the temporary that is the complete object to a subobject of which the temporary is bound persists for the lifetime of the reference except as specified below. A temporary bound to a reference member in a constructor’s ctor-initializer (12.6.2) persists until the constructor exits. A temporary bound to a reference parameter in a function call (5.2.2) persists until the completion of the full expression containing the call.

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