C++11 thread(1)

原文地址：http://www.cplusplus.com/reference/thread/thread/thread/

public member function

<thread>

std::thread::thread

default (1)initialization (2)copy [deleted] (3)move (4)

thread() noexcept;

template <class Fn, class... Args>
explicit thread (Fn&& fn, Args&&... args);

thread (const thread&) = delete;

thread (thread&& x) noexcept;

Construct thread

Constructs athreadobject:
构造一个线程对象。

(1) default constructor

Construct athreadobject that does not represent any thread of execution.

构造一个不执行任何线程的线程对象。

例子：

#include <iostream>
#include <thread>
using namespace std;
int main()
{
	thread t;	
	cout<<"t.id="<<t.get_id()<<endl;


}

运行情况：

可以看到,t是处于non-executing（未执行）状态的。

(2) initialization constructor

Construct athreadobject that represents a newjoinablethread of execution.

The new thread of execution callsfnpassingargsas arguments (usingdecay copiesof itslvalueorrvaluereferences).

The completion of this construction synchronizes with the beginning of the invocation of this copy offn.

构造一个新的可等待的线程对象。

新的线程将调用函数fn并将args传递给fn.

该构造完成与fn的复制完成同步。（即fn复制完该构造就完成了）

例子：

#include <iostream>
#include <thread>
#include <vector>
using namespace std;
void show(int n){
	cout<<"Now n is "<<n<<endl;
}
int main()
{
	int m=10;
	thread t(show,99);
	t.join();//使t能执行完
	cout<<"ok!"<<endl;
}

运行截图：

(3) copy constructor

Deleted constructor form (threadobjects cannot be copied).

默认被Delete的构造器。（线程对象不能被复制）

(4) move constructor

Construct athreadobject that acquires the thread of execution represented byx(if any). This operation does not affect the execution of the moved thread in any way, it simply transfers its handler.
Thexobject no longer represents any thread of execution.

从执行中的线程x中构造。该操作不会以任何方式影响执行中的线程，只会移交其控制权。

x不再代理任何线程的执行。

例子：

#include <iostream>
#include <thread>
#include <vector>
#include <ctime>
using namespace std;
//delay(n) 延时n秒  
void delay(double sec)  
{  
    time_t start_time, cur_time; // 变量声明  
    time(&start_time);  
    do {  
        time(&cur_time);  
        }while((cur_time - start_time) < sec );  
};  
void show(int n){
	while(n>5){
		cout<<"currentThread is "<<pthread_self()<<",Now n is "<<n<<endl;
		delay(0.5);
		n--;
	}
}
thread returnThread(){

	cout<<"returnThread start!"<<endl;
	thread t(show,10);
	delay(2); 	
	cout<<"returnThread called!"<<endl;
	return t;
}
int main()
{

	thread t2(returnThread());
	t2.join();
	cout<<"ok!"<<endl;
}

运行截图：

这是我电脑上运行一次的结果，结果不一定一样。

threadobjects that arejoinableshall either bejoinedordetachedbefore they aredestroyed.

可连接线程对象在销毁之前应该被joined或者detached.

Parameters

fn

A pointer to function, pointer to member, or any kind ofmove-constructiblefunction object (i.e., an object whose class definesoperator(), includingclosuresandfunctionobjects).

The return value (if any) is ignored.

fn为一个指向函数的指针，或者一个指向成员的的指针，甚至是任一的可以被移动构造的函数对象。

fn的返回值会被忽略。

args...

Arguments passed to the call tofn(if any). Their types shall bemove-constructible.

Iffnis amember pointer, the first argument shall be an object for which that member is defined (or a reference, or a pointer to it).

fn函数的参数。

x

threadobject whose state is moved to the constructed object.

x是一个线程对象。

FnandArgs...are template parameters: ifimplicitlydeduced, these are the properlvalueorrvaluereference type to bind the arguments to. Note though, that on the call tofnin the new thread,decay copiesoffnandargs...are always used (seestd::reffor a wrapper class that makes references copyable).

Fn,Args是模版参数，如果是隐式推导，那么这会绑定相应的左值或者右值，fn将会在新线程中被调用。

Example

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44

// constructing threads #include <iostream> // std::cout #include <atomic> // std::atomic #include <thread> // std::thread #include <vector> // std::vector std::atomic<int> global_counter (0); void increase_global (int n) { for (int i=0; i<n; ++i) ++global_counter; } void increase_reference (std::atomic<int>& variable, int n) { for (int i=0; i<n; ++i) ++variable; } struct C : std::atomic<int> { C() : std::atomic<int>(0) {} void increase_member (int n) { for (int i=0; i<n; ++i) fetch_add(1); } }; int main () { std::vector<std::thread> threads; std::cout << "increase global counter with 10 threads...\n"; for (int i=1; i<=10; ++i) threads.push_back(std::thread(increase_global,1000)); std::cout << "increase counter (foo) with 10 threads using reference...\n"; std::atomic<int> foo; for (int i=1; i<=10; ++i) threads.push_back(std::thread(increase_reference,std::ref(foo),1000)); std::cout << "increase counter (bar) with 10 threads using member...\n"; C bar; for (int i=1; i<=10; ++i) threads.push_back(std::thread(&C::increase_member,std::ref(bar),1000)); std::cout << "synchronizing all threads...\n"; for (auto& th : threads) th.join(); std::cout << "global_counter: " << global_counter << '\n'; std::cout << "foo: " << foo << '\n'; std::cout << "bar: " << bar << '\n'; return 0; }

Edit & Run

Output:

increase global counter using 10 threads...
increase counter (foo) with 10 threads using reference...
increase counter (bar) with 10 threads using member...
synchronizing all threads...
global_counter: 10000
foo: 10000
bar: 10000

Data races

Themove constructor (4)modifiesx.

Exception safety

The initialization constructor(2)throws an exception on the following conditions:
exception typeerror conditiondescription

system_error	errc::resource_unavailable_try_again	The system is unable to start a new thread

It also throws if the construction of any of the copies it makes (of thedecay typesofFnandArgs...) throws.
Depending on the library implementation, this constructor may also throw exceptions to report other situations (such asbad_allocorsystem_errorwith othererror conditions).

如果复制过程出错，会抛出system_error错误。

Note that if an exception is thrown from the function invocation (i.e., fromfnitself), it is handled by the new thread. If this invocation terminates with an uncaught exception,terminate()is called.

如果fn抛出异常，线程将会将控制权移交给新的线程，如果不捕获异常，将调用terminate.

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//写的错误或者不好的地方请多多指导，可以在下面留言或者点击左上方邮件地址给我发邮件，指出我的错误以及不足，以便我修改，更好的分享给大家，谢谢。

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author:天下无双

Email:[e-mail]

2014-9-3

于GDUT

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