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Problems creating a thread within a class.

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Started by DividedByZero May 06, 2011 12:08 AM

3 comments, last by DividedByZero 12 years, 11 months ago

DividedByZero

1,261

Author

May 06, 2011 12:08 AM

Hi guys,

I am trying to create a private CreateThread function which I can't get to compile.

error C3867: 'Thread::testThread': function call missing argument list; use '&Thread::testThread' to create a pointer to member

I have Googled this but can't understand what is going on.

#include<windows.h>

#include<iostream>



class Thread

{

public:



 Thread()

 {

 }

 ~Thread()

 {

 }



 void something()

 {

  CreateThread(0,0,testThread,0,0,0);

 }



private:

 DWORD WINAPI testThread(LPVOID args)

 {

  while(true)

  {

   std::cout<<"test\r\n";

   Sleep(500);

  }

  return 0;

 }

};

If I put DWORD WINAPI testThread(LPVOID args) outside the class it compiles ok.

I also tried CreateThread(0,0,&Thread::testThread,0,0,0);

Any help would be awesome

Brain

19,059

May 06, 2011 12:16 AM

if i remember correctly, you can't create a thread that points directly at a non-static member. Make the thread member function static, then pass 'this' in as the threads LPVOID args parameter:



#include<windows.h>

#include<iostream>



class Thread

{

public:



 Thread()

 {

 }

 ~Thread()

 {

 }



 void something()

 {

  CreateThread(0,0,&Thread::testThread, this, 0, 0);

 }



private:

 static DWORD WINAPI testThread(LPVOID args)

 {

  while(true)

  {

   std::cout<<"test\r\n";

   Sleep(500);

  }

  return 0;

 }

};

Hope this helps!

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DividedByZero

1,261

Author

May 06, 2011 12:20 AM

Spot on! You are awesome +1 to rep

Is there a general rule as to when things need to be static? This issue always gets me in trouble.

Brain

19,059

May 06, 2011 12:30 AM

There is no general rule, except that because createthread is part of the windows API and the windows API is generally C-only, it can't interact with objects/classes unless you 'flatten' them using static first.

Thanks for letting me know that it fixed it :-)

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