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Threading a Member function

Posted on 1997-07-15
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Last Modified: 2008-02-26
I am trying to create a thread from inside a class using another class member.  Here is an example of what I want to do.  The function I want to thread is of type "unsigned long _stdcall A::one(LPVOID)" which would work if I didn't have the "A::" scope operator.  Can I type cast this and remove the scope operator?
Or since the CreateThread function is not a member of the class A, it would violate the Data Abstraction that exists inside classes.  But that should be a runtime error not a compile error, right?

class A{
  one();
  unsigned long _stdcall two(LPVOID);
  int hThread;
  HANDLE ThreadID;
  };
unsigned long _stdcall A::two(LPVOID D){
  //Do Some Stuff
  }
void A::one(){
  char buff[100];
  void *data=&buff;
  hThread=CreateThread (NULL, 0, two, data, 0, &ThreadID);
  }
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Question by:lordx
2 Comments
 
LVL 23

Accepted Solution

by:
chensu earned 600 total points
ID: 1165151
Make the function as a static function of class A or a global function.
class A{
...
static unsigned long _stdcall two(LPVOID);
...
};

You have to use a static function or a global function for a thread. The reason is that a member function contains an implicit parameter (the this pointer).
For example,

unsigned long _stdcall two(LPVOID);  // member function of class A

is actually

unsigned long _stdcall two(class A *pThis, LPVOID);

if it is not a static function. And this prototype does not conform to what CreateThread() requires.  

You can pass some data that the thread needs into the structure pointed by LPVOID pParam.
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Expert Comment

by:md041797
ID: 1165152
What I usually do in this type of situation is to use a global function that's a frind of the class.  Then I pass the object in as the data and then cast it to a "SurrogateThis".
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