网上关于信号量和锁的区别，写的比较官方晦涩难懂，对于这个知识点吸收难，通过示例，我们看到信号量，可以控制同一时刻的线程数量，就算同时开启很多线程，依然可以的达到线程数可控

#include <iostream>
#include <thread>
#include <vector>
#include <semaphore.h>sem_t sem;
int shared_resource = 0;void thread_func(int id) {sem_wait(&sem); // P操作shared_resource++;std::cout << "Thread " << id << " incremented shared_resource to " << shared_resource << std::endl;std::this_thread::sleep_for(std::chrono::seconds(1)); // 模拟工作sem_post(&sem); // V操作
}int main() {const int num_threads = 20000;sem_init(&sem, 0, 2); // 初始化信号量，最大值为2std::vector<std::thread> threads;for (int i = 0; i < num_threads; ++i) {threads.push_back(std::thread(thread_func, i));}for (auto& t : threads) {t.join();}sem_destroy(&sem);return 0;
}

经过多轮测试，线程安全还是得依赖锁