蓝桥ROS机器人之现代C++学习笔记7.2 互斥量与临界区

Posted 2022-04-26 zhangrelay

看如下三段代码：

// mutex example
#include <iostream>       // std::cout
#include <thread>         // std::thread
#include <mutex>          // std::mutex

std::mutex mtx;           // mutex for critical section

void print_block (int n, char c) 
  // critical section (exclusive access to std::cout signaled by locking mtx):
  mtx.lock();
  for (int i=0; i<n; ++i)  std::cout << c; 
  std::cout << '\\n';
  mtx.unlock();


int main ()

  std::thread th1 (print_block,50,'*');
  std::thread th2 (print_block,50,'$');

  th1.join();
  th2.join();

  return 0;

---

#include <iostream>
#include <mutex>
#include <thread>

int v = 1;

void critical_section(int change_v) 
    static std::mutex mtx;
    std::lock_guard<std::mutex> lock(mtx);

    // do contention operations
    v = change_v;

    // mtx will be destructed when exit this region


int main() 
    std::thread t1(critical_section, 2), t2(critical_section, 3);
    t1.join();
    t2.join();

    std::cout << v << std::endl;
    return 0;

---

#include <iostream>
#include <mutex>
#include <thread>

int v = 1;

void critical_section(int change_v) 
    static std::mutex mtx;
    std::unique_lock<std::mutex> lock(mtx);
    // do contention operations
    v = change_v;
    std::cout << v << std::endl;
    // release the lock
    lock.unlock();

    // during this period,
    // others are allowed to acquire v

    // start another group of contention operations
    // lock again
    lock.lock();
    v += 1;
    std::cout << v << std::endl;


int main() 
    std::thread t1(critical_section, 2), t2(critical_section, 3);
    t1.join();
    t2.join();
    return 0;

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尝试编译无果……

查一下，c++20应该可以。

 

只能使用如下链接：

coliru.stacked-crooked.com

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