C++11 的線程庫問題

[emyueguang]

使用C++11的線程庫，這個地方很不理解，為什麼獲取到的線程ID都是一樣的呢


這是結果，前面一個數值是使用std::this_thread::get_id()獲取到的值，後面一個是使用GetCurrentThreadId()獲取到的，可以看出來，計算結果真真切切的是三個不同的線程在做，但是使用C++11線程庫獲取到的線程ID有的卻是一樣的。為什麼呢？

[emyueguang]

#include <thread>
#include "win32_sem.h"

uint32_t	sem = create_semaphore(0, INT32_MAX);

void process_packet()
{
	printf("thread :%d	begin process data. \n", std::this_thread::get_id());
	for (uint64_t i = 0; i < UINT64_MAX; ++i);
	printf("thread: %d	process data over. \n", std::this_thread::get_id());
}

void extract_packet()
{	
	while (true)
	{		
		printf("thread:%d - %d wait data coming ... \n", std::this_thread::get_id(), ::GetCurrentThreadId());
		wait_semaphore(sem, INFINITE);
		printf("thread:%d - %d receive data. \n", std::this_thread::get_id(), ::GetCurrentThreadId());

		// get data from array

		process_packet();
	}
}

void test_cpp_thread()
{
	std::thread	t(extract_packet);
	t.detach();
	std::thread	t2(extract_packet);
	t2.detach();
	std::thread	t3(extract_packet);
	t3.detach();
		
	release_semaphore(sem, 3);	

	std::this_thread::sleep_for(std::chrono::seconds(5));

	release_semaphore(sem, 1);

	std::this_thread::sleep_for(std::chrono::seconds(5));
	
	release_semaphore(sem, 1);
}

int main()
{	
	test_cpp_thread();
	system("pause");
	return 0;
}

[ri_aje]

引用 2 楼 emyueguang 的回复:

#include <thread>
#include "win32_sem.h"

uint32_t	sem = create_semaphore(0, INT32_MAX);

void process_packet()
{
	printf("thread :%d	begin process data. \n", std::this_thread::get_id());
	for (uint64_t i = 0; i < UINT64_MAX; ++i);
	printf("thread: %d	process data over. \n", std::this_thread::get_id());
}

void extract_packet()
{	
	while (true)
	{		
		printf("thread:%d - %d wait data coming ... \n", std::this_thread::get_id(), ::GetCurrentThreadId());
		wait_semaphore(sem, INFINITE);
		printf("thread:%d - %d receive data. \n", std::this_thread::get_id(), ::GetCurrentThreadId());

		// get data from array

		process_packet();
	}
}

void test_cpp_thread()
{
	std::thread	t(extract_packet);
	t.detach();
	std::thread	t2(extract_packet);
	t2.detach();
	std::thread	t3(extract_packet);
	t3.detach();
		
	release_semaphore(sem, 3);	

	std::this_thread::sleep_for(std::chrono::seconds(5));

	release_semaphore(sem, 1);

	std::this_thread::sleep_for(std::chrono::seconds(5));
	
	release_semaphore(sem, 1);
}

int main()
{	
	test_cpp_thread();
	system("pause");
	return 0;
}

懒得为了试这个还跑到 windows 底下。写了个例子：

#include <iostream>
#include <thread>

void function ()
{
 std::cout << std::this_thread::get_id() << std::endl;
}

int main ()
{
 std::thread    t(function);
 std::thread    t2(function);
 std::thread    t3(function);
 t .join();
 t2.join();
 t3.join();
}

试了一下没问题，输出比如： 140526880892672 140526872499968 140526864107264 可以看到三个不同的线程，你试试在你哪里一样吗。 另外，std::thread::id 应该用 std::cout 输出，printf 很可能给搞错。

[ri_aje]

代码呢？？？