C++ 线程安全备忘（Thread Safety Cheat Sheet）

中文

English

一、线程安全的概念

1. Concept of Thread Safety

线程安全指在多线程环境中，多个线程访问同一资源时，不会导致竞态条件、数据破坏或未定义行为。

Thread safety means that in a multithreaded environment, multiple threads accessing the same resource will not cause race conditions, data corruption, or undefined behavior.

简单说，就是保证程序正确性和稳定性，即使多线程同时执行相关代码。

In short, it guarantees program correctness and stability even when multiple threads execute related code simultaneously.

二、线程安全的级别

2. Levels of Thread Safety

不安全（Not thread-safe）：多线程同时访问会导致错误或竞态。

Not thread-safe: concurrent access by multiple threads can cause errors or race conditions.

线程安全（Thread-safe）：多线程访问不会产生竞态，行为正确。

Thread-safe: multiple threads can access safely without race conditions and behave correctly.

可重入（Reentrant）：函数可被多线程/中断安全调用，不依赖共享状态。

Reentrant: functions can be safely called by multiple threads or interrupts, without relying on shared state.

线程局部（Thread-local）：每个线程拥有独立变量副本，互不干扰。

Thread-local: each thread has its own copy of variables, avoiding interference.

三、C++中实现线程安全的常用方法

3. Common Ways to Achieve Thread Safety in C++

1. 互斥锁（Mutex）：用std::mutex加锁，保证同一时刻只有一个线程访问共享资源。

1. Mutex: use std::mutex to lock and ensure only one thread accesses shared resource at a time.

示例：

Example:

```cpp

```cpp

std::mutex mtx;

std::mutex mtx;

int shared_data = 0;

int shared_data = 0;

void safe_increment() {

void safe_increment() {