内联变量的多重销毁

Question

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;

...包含在两个 .cpp 文件中：

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

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

此程序打印 "deleted" 两次，这是意外的。我以为每个内联变量只有一个实例，所以我期望只有一个 "deleted".

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）只打印一次 "deleted"。

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

为了完整起见，相关标准规则（来自最新草案，强调是我加的，括号中强调的部分是我加的）：

[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]

内联变量的多重销毁

Multiple destruction of an inline variable

c++

visual-studio-2017

c++17

inline-variable