Expiring Today—Celebrate National IT Professionals Day with 3 months of free Premium Membership. Use Code ITDAY17

x
?
Solved

Threading a Member function

Posted on 1997-07-15
2
Medium Priority
?
854 Views
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);
  }
0
Comment
Question by:lordx
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
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.
0
 
LVL 4

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".
0

Featured Post

Free Tool: Port Scanner

Check which ports are open to the outside world. Helps make sure that your firewall rules are working as intended.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

In days of old, returning something by value from a function in C++ was necessarily avoided because it would, invariably, involve one or even two copies of the object being created and potentially costly calls to a copy-constructor and destructor. A…
Written by John Humphreys C++ Threading and the POSIX Library This article will cover the basic information that you need to know in order to make use of the POSIX threading library available for C and C++ on UNIX and most Linux systems.   [s…
The viewer will learn how to use the return statement in functions in C++. The video will also teach the user how to pass data to a function and have the function return data back for further processing.
The viewer will learn how to user default arguments when defining functions. This method of defining functions will be contrasted with the non-default-argument of defining functions.
Suggested Courses

719 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question