_beginthread - Create New Thread

Syntax

#include <stdlib.h>   /* also in <process.h> */
int _beginthread(void (*start_address) (void *),
                     (void *)stack,
                     unsigned stack_size,
                     void *arglist);

Description

• beginthread creates a new thread. It takes the following arguments:

  start_address

  This parameter is the address of the function that the newly created thread will execute. When the thread returns from that function, it is terminated automatically. You can also explicitly terminate the thread by calling _endthread.
  stack
  This parameter is ignored, but is retained to ease migration of C/2 programs. The C/2 compiler requires the second parameter to be the address of the bottom of the stack that the new thread will use. Because the OS/2 operating system automatically takes care of stack allocation, the parameter is not needed.
  stack_size
  The size of the stack, in bytes, that is to be allocated for the new thread. The stack size should be a nonzero multiple of 4K and a minimum of 8K. Memory is used when needed, one page at a time.
  arglist
  A parameter to be passed to the newly created thread. It is the size of a pointer, and is usually the address of a data item to be passed to the new thread, such as a char string. It provides _beginthread with a value to pass to the child thread. NULL can be used as a placeholder.

  An alternative to this function is the OS/2 DosCreateThread function. If you use DosCreateThread, you must also use a #pragma handler statement for the thread function to ensure proper C exception handling. You should also call the _fpreset function at the start of the thread to preset the 387 control status word correctly. Using DosCreateThread requires that you use _endthread to terminate the thread.

Returns

If successful, _beginthread returns the thread ID number of the new thread. It returns -1 to indicate an error.

Example Code

This example uses _beginthread to start a new thread bonjour, which prints Bonjour! five times and then implicitly ends itself. The program then prints a statement indicating the thread identifier number for bonjour.

#define  INCL_DOS#include <os2.h>
#include <stdio.h>
#include <stdlib.h>

static int wait = 1;

void bonjour(void *arg)
{
   int i = 0;

   while (wait)              /* wait until the thread id has been printed     */
      DosSleep(0l);
   while (i++ < 5)
      printf("Bonjour!\n");
}

int main(void)
{
   int tid;

   tid = _beginthread(bonjour, NULL, 8192, NULL);
   if (-1 == tid) {
      printf("Unable to start thread.\n");
      return EXIT_FAILURE;
   }
   else {
      printf("Thread started with thread identifier number %d.\n", tid);
      wait = 0;
   }
   DosWaitThread((PTID)&tid, DCWW_WAIT);  /* wait for thread bonjour to       */
                                          /* end before ending main thread    */

   return 0;

   /****************************************************************************
      The output should be similar to :

       Thread started with thread identifier number 2.
       Bonjour!
       Bonjour!
       Bonjour!
       Bonjour!
       Bonjour!
   ****************************************************************************/
}

Related Information

• endthread
  
• threadstore

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