c++ - 内联变量的多次销毁

Question

这个问题在这里已经有了答案:





inline variable is initialized more than once

(3 个回答)


1年前关闭。




这是一个包含内联变量的头文件:

// inline.hpp
#pragma once

#include <iostream>

struct Test {
    ~Test() { std::cout << "deleted" << std::endl; }
};

inline const Test test;

...分为两个 .cpp文件:

// usage.cpp
#include "inline.hpp"

// main.cpp
#include "inline.hpp"
auto main() -> int { return 0; }

该程序打印“已删除”两次，这是出乎意料的。
我认为每个内联变量只有一个实例，所以我期望只有一个“删除”。

这是编译器的错误吗？还是我做错了什么？

代码是用VS2017编译的。

Answer 1

Is this a bug of compiler?

据我所知，是的。 GCC 和 Clang(以及根据评论的 VS2019)仅打印“已删除”一次。

命名空间范围内的非 volatile const 内联变量具有外部链接。您描述的行为似乎暗示了内部链接，这是编译器的错误行为。

为完整起见，相关标准规则(来自最新草案，我添加的重点，我添加的括号中的强调部分):

[basic.link]

A name having namespace scope has internal linkage if it is the name of

• ... explicitly declared static; [does not apply] or

• a non-template variable of non-volatile const-qualified type, [applies...] unless

  • ...
  • it is inline or exported, [exception applies] or

... A name having namespace scope that has not been given internal linkage above [applies] and that is the name of

• a variable; [applies] or

• ...

has its linkage determined as follows:

• if the enclosing namespace has internal linkage, the name has internal linkage; [does not apply]

• otherwise, if the declaration of the name is attached to a named module ... [does not apply]

• otherwise, the name has external linkage. [applies]