April 2018
Intermediate to advanced
303 pages
4h 54m
Chinese
Content preview from Effective Modern C++（中文版）
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254
｜
第
7
章
std::vector<std::thread> vt;
//
反应任务的容器
for (int i = 0; i < threadsToRun; ++i) {
vt.emplace_back([
sf
]{ sf.wait();
// sf
局部副本之上的
wait
react(); });
//
关于
emplace_back
，参见条款
42
}
…
//
若此“…”抛出异常，则
detect
会失去响应！
p.set_value();
//
让所有线程取消暂停
…
for (auto& t : vt) {
//
把所有线程置为不可联结状态
t.join();
//
欲知“
auto&
”详情，参见条款
2
}
}
使用期值的设计能够实现这样的效果，此事实值得注意，这也是为何应该将一次性事
件通信纳入考量。
要点速记
•
如果仅为了实现平凡事件通信，基于条件变量的设计会要求多余的互斥量，
这会给相互关联的检测和反应任务带来约束，并要求反应任务校验事件确
已发生。
•
使用标志位的设计可以避免上述问题，但这一设计基于轮询而非阻塞。
•
条件变量和标志位可以一起使用，但这样的通信机制设计结果不甚自然。
•
使用
std::promise
型别对象和期值就可以回避这些问题，但是一来这个途
径为了共享状态需要使用堆内存，而且仅限于一次性通信。
条款
40
：对并发使用
std::atomic
，对特种内存
使用
volatile
可怜的
volatile ...
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I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.