g++ -Wreorder 的意义何在?

问题描述

g++ -Wall 选项包括 -Wreorder.该选项的作用如下所述.我不清楚为什么有人会关心(尤其是在 -Wall 中默认打开它).

-Wreorder(仅限 C++)当代码中给出的成员初始化器的顺序不正确时发出警告匹配它们必须执行的顺序.例如:结构 A {诠释我;诠释 j;A(): j (0), i (1) { }};编译器会将 i 和 j 的成员初始化器重新排列为匹配成员的声明顺序，发出警告影响.此警告由 -Wall 启用.

解决方案

考虑:

结构 A {诠释我;诠释 j;A() : j(0), i(j) { }};

现在 i 被初始化为某个未知值，而不是零.

另外，i 的初始化可能会产生一些副作用，这对顺序很重要.例如

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

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.

解决方案

Consider:

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

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

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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