Thread-Safety of Static Local Variable in C++

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已于 2022-05-10 00:00:08 修改

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于 2022-05-09 23:59:52 首次发布

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C++11标准确保了静态局部变量的线程安全性。在多线程环境中，这些变量只初始化一次。本文通过一个简化示例解释了静态局部变量的行为，并深入到编译后的代码，展示了如何使用原子操作实现线程安全初始化。

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Introduction

Since C++11, static local variable has been made sure to be thread safe by C++11 standard. In singleton for example, static keyword is often used to extend the life time of local variable to the end of program and initialized only once. What’s interesting is the behavior of static local variable in multi-thread environment.

Example

#include <iostream>
#include <thread>
#include <vector>

using namespace std;

int init() {
   
	cout << "init here" << endl;
	return 5;
}

int get_singleton() {
   
	static int singleton = init();
	return singleton;
}

int main() {
   
	vector<thread> ts(10);
	for (int i = 0; i < 10; i++) {
   
		ts[i] = thread([]() {
   
			int a = get_singleton();
		});
	}
	for (int i =