以下示例给出的构造有什么不幸? [英] What is unfortunate about the construction given in the following example?

问题描述

"15.6.2初始化基和成员"(N4713)节具有以下第11项的示例:

Section "15.6.2 Initializing bases and members" (N4713) has the following example following item 11:

struct A {
    A() = default; // OK
    A(int v) : v(v) { } // OK
    const int& v = 42; // OK
};
A a1; // error: ill-formed binding of temporary to reference
A a2(1); // OK, unfortunately

示例最后一行中的构造有什么不幸?

What is unfortunate about the construction in the last line of the example?

我在整个参考书中搜索了其他允许的不幸"行为的出现，但没有找到.

I searched the whole reference for other occurrences of "unfortunate" behaviour that were permitted but I could find none.

如果在此特定情况下不幸，是否可以将其定为非法?

If it was unfortunate in this particular context, could it not have been made illegal?

推荐答案

在两种情况下， A :: v 都是悬空引用(临时取自42，或者是参数 v 的构造函数).

In both case A::v is dangling reference (temporary from 42, or parameter v of constructor).

在某些情况下，引用临时文件(甚至延长使用寿命)可能是合法的，并且可以正确使用.

Having reference to temporary (even with extended lifetime) might be legal and correctly used in some cases.

很难发现所有滥用案例以禁止它们.

Hard to detect all misuse cases to forbid them.

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