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Linux 程序员都用过 Pthread, 但有了 C++11 的 std::thread以后，你可以在语言层面编写多线程程序了，直接的好处就是多线程程序的可移植性得到了很大的提高，所以作为一名 C++ 程序员，熟悉 C++11 的多线程编程方式还是很有益处的。
C++11 新标准中引入了四个头文件来支持多线程编程，他们分别是<atomic> ,<thread>,<mutex>,<condition_variable>和<future>。
下面是一个最简单的使用 std::thread 类的例子：
#include#include #include // std::cout#include // std::threadvoid thread_task() { std::cout << "hello thread" << std::endl;}int main(int argc, const char *argv[]){ std::thread t(thread_task); t.join(); return EXIT_SUCCESS;}
Makefile 如下：
all:ThreadCC=g++CPPFLAGS=-Wall -std=c++11 -ggdbLDFLAGS=-pthreadThread:Thread.o $(CC) $(LDFLAGS) -o $@ $^Thread.o:Thread.cc $(CC) $(CPPFLAGS) -o $@ -c $^
注意在 Linux GCC4.6 环境下，编译时需要加 -pthread，否则执行时会出现：
$ ./Threadterminate called after throwing an instance of 'std::system_error' what(): Operation not permittedAborted (core dumped)
原因是 GCC 默认没有加载 pthread 库，据说在后续的版本中可以不用在编译时添加 -pthread 选项。
std::thread 在 <thread> 头文件中声明，因此使用 std::thread 时需要包含 <thread> 头文件。
| default (1) | thread() noexcept; |
|---|---|
| initialization (2) | template |
| copy [deleted] (3) | thread (const thread&) = delete; |
| move (4) | thread (thread&& x) noexcept; |
std::thread 各种构造函数例子如下：
#include#include #include #include #include #include void f1(int n){ for (int i = 0; i < 5; ++i) { std::cout << "Thread " << n << " executing\n"; std::this_thread::sleep_for(std::chrono::milliseconds(10)); }} void f2(int& n){ for (int i = 0; i < 5; ++i) { std::cout << "Thread 2 executing\n"; ++n; std::this_thread::sleep_for(std::chrono::milliseconds(10)); }} int main(){ int n = 0; std::thread t1; // t1 is not a thread std::thread t2(f1, n + 1); // pass by value std::thread t3(f2, std::ref(n)); // pass by reference std::thread t4(std::move(t3)); // t4 is now running f2(). t3 is no longer a thread t2.join(); t4.join(); std::cout << "Final value of n is " << n << '\n';}
| move (1) | thread& operator= (thread&& rhs) noexcept; |
|---|---|
| copy [deleted] (2) | thread& operator= (const thread&) = delete; |
请看下面的例子：
#include#include #include // std::chrono::seconds#include // std::cout#include // std::thread, std::this_thread::sleep_forvoid thread_task(int n) { std::this_thread::sleep_for(std::chrono::seconds(n)); std::cout << "hello thread " << std::this_thread::get_id() << " paused " << n << " seconds" << std::endl;}int main(int argc, const char *argv[]){ std::thread threads[5]; std::cout << "Spawning 5 threads...\n"; for (int i = 0; i < 5; i++) { threads[i] = std::thread(thread_task, i + 1); } std::cout << "Done spawning threads! Now wait for them to join\n"; for (auto& t: threads) { t.join(); } std::cout << "All threads joined.\n"; return EXIT_SUCCESS;}
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