C++11 中的新特性

C++11 新加入的特性

C++11 新特性学习笔记：
default 和 delete 修饰特殊成员函数。

Defaulted and Deleted function

Asynchronous Programming

以下三点都满足时， std::future 析构可能导致阻塞：

1. 共享状态是在调用 std::async 时创建的；
2. 共享状态尚未处于 std::future_status::read 状态；
3. 被析构的当前对象持有共享状态的最后一个引用。

获取 std::future 结果的方法：

1. std::future::get()            阻塞当前线程，等待异步操作完成并返回异步执行结果。
2. std::future::wait()          阻塞当前线程，等待异步操作完成，无返回值。
3. std::future::wait_for()    阻塞当前线程，超时等待异步操作完成，返回异步操作执行状态。
4. std::future::wait_until()  阻塞当前线程，等待异步操作完成直到指定的时间点。

Name Description
future::get Retrieves the result that is stored in the associated asynchronous state.
future::wait Blocks the current thread until the associated asynchronous state is ready.
future::wait_for Blocks until the associated asynchronous state is ready
or until the specified time has elapsed.
future::wait_until Blocks until the associated asynchronous state is ready or until a specified point in time.

与 std::future 相关的枚举类型：
  • std::future_errc
label value description
broken_promise 0 The promise object with which the future shares its shared state was destroyed before being set a value or an exception.
future_already_retrieved 1 A future object was already retrieved from this provider.
promise_already_satisfied 2 The promise object was already set a value or exception.
no_state 3 An operation attempted to access the shared state of an object with no shared state.
  • std::future_status
label value description
future_status::ready 0 The function returned because the shared state was ready.
future_status::timeout 1 The function returned because the specified time was exhausted.
future_status::deferred 2 The function returned because the shared state contains a deferred function (see std::async).
  • std::launch
label value description
launch::async 0x1(vc) Asynchronous: The function is called asynchronously by a new thread and synchronizes its return with the point of access to the shared state.
launch::deferred 0x2(vc) Deferred: The function is called at the point of access to the shared state.

Reference and Forwarding

为什么C++11引入了std::ref？
C++11尝鲜：右值引用和转发型引用

Lambda Expression

Lambda 表达式中的闭包说明
语法 说明
[a, &b] 其中a以复制捕获，b以引用捕获
[this] 以引用捕获当前对象(*this)
[&] 以引用捕获所有用于 lambda 体内的自动变量，并以引用捕获当前对象，若存在
[=] 以复制捕获所有用于 lambda 体内的自动变量，并以引用捕获当前对象，若存在
[] 不捕获
&, x x显式的捕获，其他变量按引用捕获。
=, &z z按引用捕获，其他变量按值捕获。

留言

▲