g ++ -Wreorder的意义是什么？ [英] What's the point of g++ -Wreorder?

问题描述

g ++ -Wall选项包括-Wreorder。此选项的作用如下所述。这是不明显的，为什么有人会关心（特别是足以打开在默认情况下在-Wall）。

The g++ -Wall option includes -Wreorder. What this option does is described below. It is not obvious to me why somebody would care (especially enough to turn this on by default in -Wall).

-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, emit-ting a warning to that
  effect.  This warning is enabled by -Wall.

推荐答案

请考虑：

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

现在 i 初始化为某个未知值，而不是零。

Now i is initialized to some unknown value, not zero.

或者， i 的初始化可能有一些副作用，例如

Alternatively, the initialization of i may have some side effects for which the order is important. E.g.

A(int n) : j(n++), i(n++) { }

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