我正在为 c++11 编写一个带有简单信号量实现的消费者/生产者类。但是，以下代码无法编译。如果我删除producer_consumer类和makeproducer和consumer全局函数，并将线程创建部分（std::thread t1(consumer), t2(consumer); t1.join(); t2.join();）移动到main函数中，它可以编译，但实现仍然不正确，最终会导致分段错误。如何更正代码？谢谢。
#include <iostream>
#include <thread>
#include <mutex>
class semaphore {
private:
std::mutex m;
std::condition_variable cond;
unsigned long n;
public:
semaphore(int i) : n(i) {}
void up() {
std::unique_lock <std::mutex> lock (m);
++n;
cond.notify_one();
}
void down() {
std::unique_lock <std::mutex> lock (m);
while(!n) cond.wait(lock);
--n;
}
};
class producer_consumer{
private:
semaphore full, empty;
int i = 0;
std::thread t1, t2;
public:
producer_consumer(int n): full(0), empty(n), i(0){}
void run(){
t1 = std::thread(&producer_consumer::producer, *this);
t2 = std::thread(&producer_consumer::consumer, *this);
}
void stop(){
t1.join();
t2.join();
}
void producer (){
while (true){
empty.down();
i ++;
std::cout << "[p]" << i << std::endl;
full.up();
}
}
void consumer (){
while (true){
full.down();
i --;
std::cout << "[c]" << i << std::endl;
empty.up();
}
}
};
int main(){
producer_consumer pc(5);
pc.run();
pc.stop();
return 0;
}
我使用 clang++ 编译文件：
clang++ -std=c++0x -stdlib=libc++ pc.cpp ; ./a.out
错误信息：
In file included from file_name.cpp:1:
In file included from /usr/bin/../lib/c++/v1/iostream:38:
In file included from /usr/bin/../lib/c++/v1/ios:216:
In file included from /usr/bin/../lib/c++/v1/__locale:15:
In file included from /usr/bin/../lib/c++/v1/string:434:
In file included from /usr/bin/../lib/c++/v1/algorithm:591:
/usr/bin/../lib/c++/v1/type_traits:1423:12: error: call to implicitly-deleted
copy constructor of 'typename decay<producer_consumer &>::type'
(aka 'producer_consumer')
return _VSTD::forward<_Tp>(__t);
^~~~~~~~~~~~~~~~~~~~~~~~
更新：@DanqiWang 通过更改*this为this. 现在看来，信号量不能正常工作，最终会使程序崩溃：
./a.out
[p]1
[p]2
[p]3
[p]4
[p]5
....
[p]2
[p]3
[p]4
1
[c]3
[p[]c3]
3
[[c]3
p][2c
][p]3
[p]4
4
[c]3
[c]2
Segmentation fault: 11