pthread_create参数函数指针 [英] pthread_create parameter function pointer

问题描述

我试图在下面的代码中创建一个线程，但指向pthread_create方法调用的函数参数的指针只是不让我编译我的代码。

请让我知道我在做什么错误，以及如何在以下代码中修复它：

  #includeRobotNodes.cpp
 
 int main（int argc，char ** argv）{
 
 int i，numRobotsToInit = 7 ; 
 
 //声明运行函数指针
 void（* run）（）; 
 
 //创建机器人节点数组
 RobotNodes * robots [numRobotsToInit]; 
 
 // init robot nodes 
 for（i = 0; i  robots [i] = new RobotNodes（i，0.2，0.2） 
} 
 
 
 for（i = 0; i  run =& robots [i] 
 pthread_t thread; 
 pthread_create（& thread，NULL，（void *（*）（void *））run，NULL）; 
} 
} 
  

我得到的错误如下：
错误：需要作为一元&'操作数的$值$ / code>

编辑：run类RobotNodes.cpp包含在此类的顶部。

解决方案

似乎有一个非静态 RobotNodes 中的成员函数，你似乎认为成员函数的类型是 void（*）（）。如果是这样，那么你错了。

成员函数和自由函数的类型不相同，即使它们具有完全相同的签名！

所以我建议你定义一个名为 start 的静态函数：

  class RobotNodes 
 {
 public：
 void run（）; //定义它像你喜欢
 
 static void * start（void * pdata）
 {
 RobotNodes * robot = static_cast< RobotNodes *>（pdata）; 
 robot-> run（）; // forward it 
 return 0; //或返回为文档说
} 
}; 
  

然后使用开始： >

  std :: vector< pthread_t>线程（numRobotsToInit）; 
 for（i = 0; i  {
 pthread_create（& threads [i]，NULL，RobotNodes :: start，& robots [i]）; 
} 
  

另外，注意我创建了一个 pthread_t 在循环外;这是因为如果它们是不同的线程，每个线程实例必须不同，此外，即使循环停止后，每个线程实例必须继续存在。

I am trying to create a thread in the following code but the pointer to a function parameter of the pthread_create method call is just not letting me compile my code.

Please let me know what I am doing wrong and how can I fix it in the following code:

#include "RobotNodes.cpp"

int main(int argc, char** argv){

int i, numRobotsToInit = 7;

//declare run function pointer
void (*run)();

//create array of robot nodes 
RobotNodes* robots[numRobotsToInit]; 

//init robot nodes
for(i = 0; i<numRobotsToInit; i++){
    robots[i] = new RobotNodes(i, 0.2, 0.2);
}


for(i = 0; i<numRobotsToInit; i++){
        run = &robots[i]->run;
        pthread_t thread; 
    pthread_create(&thread, NULL, (void*(*)(void*))run, NULL);       
}
}

The error that I get is the following: error: lvalue required as unary ‘&’ operand

Edit: run() is a method from class RobotNodes.cpp that is included on the top of this class.

解决方案

There seems to be a non-static member function in the class RobotNodes and you seem to think that the type of member function is void (*)(). If so, then you are wrong.

The type of non-static member functon and free function are not same, even if they have exactly same signature!

So I would suggest you to define a static function called start, as:

class RobotNodes
{
   public:
        void run(); //define it as you like

        static void* start(void *pdata)
        {
             RobotNodes *robot = static_cast<RobotNodes*>(pdata);
             robot->run(); //forward it
             return 0; //or return as the documentation says
        }
};

Then use start as :

std::vector<pthread_t> threads(numRobotsToInit);
for(i = 0; i<numRobotsToInit; i++)
{
    pthread_create(&threads[i], NULL, RobotNodes::start, &robots[i]);       
}

Also, notice that I have created a vector of pthread_t outside the loop; it is because each thread instance has to be different if they are different thread, and furthermore, each thread instance must continue to exist even after the loop stops.

这篇关于pthread_create参数函数指针的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！