如何用pthreads多线程类成员函数？ [英] How to multithreading a class member function with pthreads?

问题描述

我试图在多线程中从名为 SVAnchor 的类运行名为 extensionStep 的函数。我使用这个代码：

  rc = pthread_create（& threads [i]，NULL，extensionStep，& td [i] ）; 
  

来调用函数，这里是 extensionStep ：

  void * SVAnchor :: extensionStep（void * threadarg）
  
 
 
 
，我收到以下错误：
 错误：不能将'SVAnchor :: extensionStep'从类型'void *（SVAnchor ::）（void *）'转换为类型'void *（*）（void *）''
 rc = pthread_create（& threads [i ]，NULL，extensionStep，& td [i]）; 
 ^ 
  
显示问题是从类型'void *（SVAnchor：:) （void *）'to type'void *（）（void）'
 
 
 
如何解决这个问题？
 
 
 
感谢所有
解决方案
这应该做的工作：（在使函数 extensionStep  static）
  rc = pthread_create（& threads [i]，NULL，&（SVAnchor :: extensionStep ），& td [i]）; 
  
或者您可以创建如下的包装函数：
  struct Argument {
 SVAnchor * ptr; 
 int * tid; 
} 
 
 static void * extensionStepWrapper（void * arg）
 {
 return（（（Argument *）arg） - > ptr） - & （（Argument *）arg）→tid）; 
} 
  
并使用包装器：
 参数arg; 
 arg.ptr =&（class_variable_name）; //使用适当的名称（无论你的变量名是类SVAnchor的对象）
 arg.tid =&（td [i]）; 
 
 rc = pthread_create（& threads [i]，NULL，&（SVAnchor :: extensionStepWrapper），& arg）; 
  
请注意，如果你从另一个成员函数中调用它，你可以这样做： / p> 
 
 
  arg.ptr = this; 
  
您还可以在类中创建一个方法来启动线程：
  bool StartThread（int * tid）{
 return（pthread_create（& _thread，NULL，extensionStep，tid）== 0）; 
} 
  
您可能还需要将线程作为StartThread（）函数的参数传递。 
 
I'm trying to run a function named extensionStep from a class named SVAnchor in multi threads. i use this code:
 rc = pthread_create(&threads[i], NULL, extensionStep, &td[i]);
to call the function and here is the definition of extensionStep :
void* SVAnchor::extensionStep( void *threadarg)
and i got the following error:
error: cannot convert 'SVAnchor::extensionStep' from type 'void* (SVAnchor::)(void*)' to type 'void* (*)(void*)'
           rc = pthread_create(&threads[i], NULL, extensionStep, &td[i]);
                                                                       ^
that shows the problem is converting from type 'void* (SVAnchor::)(void*)' to type 'void* ()(void)'

How to solve this problem?

Thanks all
解决方案
This should do the job: (After making the function extensionStep static)
rc = pthread_create(&threads[i], NULL, &(SVAnchor::extensionStep), &td[i]);
Or you can create a wrapper function like this:
struct Argument {
    SVAnchor* ptr;
    int* tid;
}

static void *extensionStepWrapper(void *arg)
{
    return (((Argument*)arg)->ptr)->extensionStep(((Argument*)arg)->tid);
}
And use the wrapper:
Argument arg;
arg.ptr = &(class_variable_name); // Use appropriate name (whatever you variable name is for the object of the class SVAnchor)
arg.tid = &(td[i]);

rc = pthread_create(&threads[i], NULL, &(SVAnchor::extensionStepWrapper), &arg);
Note that if you're calling this from inside another member function, you may do this instead:
arg.ptr = this; 
You can also create a method in the class to start the thread:
bool StartThread(int* tid){
      return (pthread_create(&_thread, NULL, extensionStep, tid) == 0);
}
You might also need to pass the thread as argument of StartThread() function.

                        
这篇关于如何用pthreads多线程类成员函数？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！