这些成员有没有具体的排序？ [英] Do these members have unspecified ordering?

问题描述

一位同事告诉我，在以下类型中，所有成员在记忆中都有不明的排序（相对于彼此）。

我怀疑这一点，因为他们都

$ b

  foo {public：int x; public：int y; public：int z; }; 
  

解决方案

您的同事对于C ++ 03： / p>

[C ++ 03：9.2 / 12]： （非联合）类（不包含中间访问限定符），以便稍后的成员在类对象中具有更高的地址。未指定由访问限定符分隔的非静态数据成员的分配顺序（11.1）。 [..]

但对C ++ 11来说是正确的：

[C ++ 11：9.2 / 14]：分配具有相同访问控制的类（第11条），以便以后的成员在类对象中具有较高的地址。未指定具有不同访问控制的非静态数据成员的分配顺序（11）。 [..]

A colleague told me that, in the following type, all members have unspecified ordering in memory (relative to one another).

I doubt this, because they all have the same access level.

Who is correct?

struct foo { public: int x; public: int y; public: int z; };

解决方案

Your colleague is correct for C++03:

[C++03: 9.2/12]: Nonstatic data members of a (non-union) class declared without an intervening access-specifier are allocated so that later members have higher addresses within a class object. The order of allocation of nonstatic data members separated by an access-specifier is unspecified (11.1). [..]

But you are correct for C++11:

[C++11: 9.2/14]: Nonstatic data members of a (non-union) class with the same access control (Clause 11) are allocated so that later members have higher addresses within a class object. The order of allocation of non-static data members with different access control is unspecified (11). [..]

(Spot the difference.)

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