C++ 级联破坏具有静态存储持续时间的对象

Question

this link 表示具有静态存储持续时间的对象的级联破坏是 C++ 中流行的未定义行为。究竟是什么？我不明白。如果能用一个简单的C++程序来说明就更好了。非常感谢您的帮助。谢谢

Answer 1

static_destruction.h

#include <vector>

class   first
{
public:
  static std::vector<int> data;

public:
  first();
  ~first();
};

class   second
{
public:
  static std::vector<int> data;

public:
  second();
  ~second();
};

class   container
{
public:
  static first  f;
  static second s;
};

static_destruction.cpp

#include <iostream>
#include "static_destruction.h"

first::first()
{
  data = {1, 2, 3, 4};
}

first::~first()
{
  std::cout << second::data.size() << std::endl;
}

std::vector<int>        first::data;

second   container::s;

int     main(void)
{
}

static_destruction2.cpp

#include <iostream>
#include "static_destruction.h"

second::second()
{
  data = {1, 2, 3, 4, 5, 6};
}

second::~second()
{
  std::cout << first::data.size() << std::endl;
}

std::vector<int> second::data;

first   container::f;

由于跨编译单元的静态对象的销毁顺序未定义（实际上是未定义的构造顺序但结果相同，因为销毁顺序是构造的逆序），在我的机器上取决于顺序我在其中编译文件，它给我不同的输出：

$> g++ -std=c++11 static_destruction.cpp static_destruction2.cpp
$> ./a.out
0
4

和

$> g++ -std=c++11 static_destruction2.cpp static_destruction.cpp
$> ./a.out
0
6

我相信这就是

中未定义行为的含义

Cascading destructions of objects with static storage duration

C++ 级联破坏具有静态存储持续时间的对象

C++ Cascading destructions of objects with static storage duration

c++

destructor

undefined-behavior

object-destruction

static_destruction.h

static_destruction.cpp

static_destruction2.cpp