- 在多线程程序开发中，咱们有时会心愿期待其余线程完结后在继续执行某些工作。比方常见的，主线程须要期待其余所有子线程完结后再完结程序。在Windows下咱们个别应用WaitForSingleObject，或者WaitForMultipleObjects来实现，它们都会期待Object被设置为有信号时才返回的。这样咱们在主线程完结的中央wait，在子线程完结的中央设置信号，就能实现上述性能。
然而这个API是Windows下的，无奈跨平台应用。还好C++11为咱们带来了多线程的反对。在C++11中咱们能够通过mutex和condition_variable来达到类似成果。上面是我写的小例子。
#include <iostream>#include <thread>#include <mutex>#include <condition_variable>#include <chrono>std::mutex mx;std::mutex g_mx;std::condition_variable g_cv;uint32_t g_thread_num = 0;void function_1(){ for (int i = 0; i < 100; i++) { std::lock_guard<std::mutex> loc(mx); std::cout << "from function 1:" << i << std::endl; } std::unique_lock<std::mutex> guard(g_mx); --g_thread_num; g_cv.notify_one(); guard.unlock(); std::cout << "function 1 end" << std::endl;}void function_2(){ for (int i = 0; i < 100; i++) { std::lock_guard<std::mutex> loc(mx); std::cout << "from function 2:" << i << std::endl; } std::unique_lock<std::mutex> guard(g_mx); --g_thread_num; g_cv.notify_one(); guard.unlock(); std::cout << "function 2 end" << std::endl;}void function_3(){ for (int i = 0; i < 100; i++) { std::lock_guard<std::mutex> loc(mx); std::cout << "from function 3:" << i << std::endl; } std::this_thread::sleep_for(std::chrono::seconds(3)); std::unique_lock<std::mutex> guard(g_mx); --g_thread_num; g_cv.notify_one(); guard.unlock(); std::cout << "function 3 end" << std::endl;}int main(){ std::thread t1(function_1); { std::unique_lock<std::mutex> guard(g_mx); ++g_thread_num; } t1.detach(); std::thread t2(function_2); { std::unique_lock<std::mutex> guard(g_mx); ++g_thread_num; } t2.detach(); std::thread t3(function_3); { std::unique_lock<std::mutex> guard(g_mx); ++g_thread_num; } t3.detach(); for (int i = 0; i < 100; i++) { std::lock_guard<std::mutex> loc(mx); std::cout << "from function main:" << i << std::endl; } { std::unique_lock<std::mutex> guard(g_mx); g_cv.wait(guard, []() { return g_thread_num == 0; }); } std::cout << "main end" << std::endl; return 0;}- 例子写的很简略，其实能够简略封装下会更好用。大家如果有什么更好的解决方案也欢送交换。