We help IT Professionals succeed at work.

Threads with C++

Robert888
Robert888 asked
on
Medium Priority
686 Views
Last Modified: 2013-12-03
Hi,

Using Visual C++ and the CreateThread function I have a problem with member functions.  If i call CreateThread
as follows

hconin = ::CreateThread(NULL,0,
      (LPTHREAD_START_ROUTINE)                                 WorkerThread,
      0,
      CREATE_SUSPENDED,
      &id);

Where WorkerThread is a global function everything is OK.
But if I define WorkerThread to be a member function of the Class that is calling CreateThread i get an error at compile time.  

error C2440: 'type cast' : cannot convert from 'overloaded function type' to 'unsigned long (__stdcall *)(void *)'

Anyone any ideas

Thanks

Robert

Comment
Watch Question

Commented:
Thats because a pointer to a normal member function takes a "this" pointer (changing the signature of the function).  You should use a static member function as the address passed to CreateThread(), pass the "this" pointer instead of "0", cast
the this pointer in the static function to your class type and
then call the non-static member function.  For example:

class MyThread {
  void ActualThreadFunction();
 
  static void StaticThreadFunction(void *ptr)
  {
    MyThread * myThread = reinterpret_cast<MyThread *>(ptr);
    myThread->ActualThreadFunction();
  }
 
  void Start()
  {
    // ...
    CreateThread(NULL,0,
      (LPTHREAD_START_ROUTINE)StaticThreadFunction,
      this,CREATE_SUSPENDED,&id);
    // ...
  }
};

Also, (this for free) you _really_should_ (really) use
_threadbeginex() instead of CreateThread() to avoid resource
leaks.

Not the solution you were looking for? Getting a personalized solution is easy.

Ask the Experts
Access more of Experts Exchange with a free account
Thanks for using Experts Exchange.

Create a free account to continue.

Limited access with a free account allows you to:

  • View three pieces of content (articles, solutions, posts, and videos)
  • Ask the experts questions (counted toward content limit)
  • Customize your dashboard and profile

*This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.

OR

Please enter a first name

Please enter a last name

8+ characters (letters, numbers, and a symbol)

By clicking, you agree to the Terms of Use and Privacy Policy.