标准是否保证初始化顺序？ [英] Is the order of initialization guaranteed by the standard?

问题描述

在下面的代码片段中，d1的初始值设定项传递了尚未构造的d2（正确吗？），所以D的复制构造函数中的dj是未初始化的内存访问吗？

In the following code snippet d1's initializer is passed d2 which has not been constructed yet (correct?), so is the d.j in D's copy constructor an uninitialized memory access?

struct D
{
    int j;

    D(const D& d) { j = d.j; }
    D(int i) { j = i; }
};

struct A
{
    D d1, d2;
    A() : d2(2), d1(d2) {}
};

C ++标准的哪一部分讨论了数据成员的初始化顺序？

Which section of C++ standard discusses order of initialization of data members?

推荐答案

我现在没有标准的方便工具，所以我无法引用该部分，但是结构或类成员的初始化总是 以声明的顺序发生。在构造函数初始化程序列表中提到成员的顺序无关。

I don't have the standard handy right now so I can't quote the section, but structure or class member initialisation always happens in declared order. The order in which members are mentioned in the constructor initialiser list is not relevant.

Gcc发出警告 -Wreorder 当顺序不同时发出警告：

Gcc has a warning -Wreorder that warns when the order is different:

       -Wreorder (C++ only)
           Warn when the order of member initializers given in the code does
           not match the order in which they must be executed.  For instance:

                   struct A {
                     int i;
                     int j;
                     A(): j (0), i (1) { }
                   };

           The compiler will rearrange the member initializers for i and j to
           match the declaration order of the members, emitting a warning to
           that effect.  This warning is enabled by -Wall.

这篇关于标准是否保证初始化顺序？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！