Re: out of scope pointers in threads

From:

"Maic Schmidt" <privat@maicschmidt.de>

Newsgroups:

comp.lang.c++

Date:

Fri, 28 Nov 2008 23:25:51 +0100

Message-ID:

<49306ff1$1@news.arcor-ip.de>

Your pointer seems to go "out of scope" because your procedure where you
declared the pointer ends,
and so its local variable stack is cleared.

Declare your data-pointer at class or global scope.

class SVDaemon
{
  public:
    void StartThread()
    {
        pointer = new MyData();
        wndThread =
CreateThread(NULL,0,(LPTHREAD_START_ROUTINE)WindowThread,pointer,0,&threadId
);
    }
  private:
    MyData* pointer;
    DWORD threadId;
    HANDLE wndThread;
    static DWORD WindowThread(MyData* data);
};

Greetz
Maic

"uche" <uraniumore235@hotmail.com> schrieb im Newsbeitrag
news:c201d729-47c7-449f-9d11-62ac37d10255@a29g2000pra.googlegroups.com...

On Nov 28, 10:51 am, uche <uraniumore...@hotmail.com> wrote:

I am trying to send a pointer to the thread below; however, when the
thread gets executed, the pointer goes out of scope . How do I fix
it ?

int mywrite(char* id, int number_of_characters, char char_array)
{
  HANDLE Producer;

  DWORD ThId;

  //global_char = char_array;

  //create mutual exlusion for producer process to write into the
buffer

  //create producer thread and start the function for inserting
characters
  //mywriteTh is the entry point of the producer

  ptr =new data;
  ptr->character = char_array;
  cout<<ptr->character<<endl;
  ptr->id = id;
  cout<<ptr->id<<endl;

  Producer = (HANDLE) CreateThread (NULL, 0, mywriteTh,
reinterpret_cast<data> (ptr) , 0, &ThId); // i want to send the
pointer to this thread

  cout<<ptr->id<<endl;

  return 0;

}

DWORD WINAPI mywriteTh(data ptr)
{
//global_char is available here

DWORD tId = GetCurrentThreadId();

data *ptr_data = reinterpret_cast<data *>(ptr); // pointer is goes
out of scope

}

please note: change data* to LPVOID ... HOWEVER, THIS DOESN'T SEEM TO
DO THE TRICK! I STILL GET A POINTER THAT IS OUT OF SCOPE!