c++多線程，lock_guard

template<class Mutex> class lock_guard;

lock_guard

是一個一直使互斥量鎖定的管理鎖對象；

在構建階段，互斥量被調用線程鎖定，在析構階段，鎖unlocked

lock_guard是最簡單的鎖，對具有自動持續時間的對象特別有用，該i持續時間能一直持續到上下文結束；

 

 #include <iostream>
 #include <mutex>
 #include <thread>
 #include <stdexcept>
 
 using namespace std;
 mutex mtx;
 
 void PrintEven(int x) {
     if (x % 2 == 0) {
         cout<< x<< " is even"<<endl;
     } else {
         throw(logic_error("not even"));
     }
 }
 
 void PrintThreadId(int x) {
     try {
         //using local lock_guard to lock mtx
         //guarantees unlocking on destruction/exception
         lock_guard<mutex> lck(mtx);
         PrintEven(x);
     } catch (logic_error&) {
         cout<<" exception caught."<<endl;
     }
 }
 
 int main(void) {
     thread threads[10];
     for (int i = 0; i < 10; ++i) {
         threads[i] = thread(PrintThreadId, i + 1);
     }
     for (auto& t : threads) {
         t.join();
     }
     return 0;
 }