KEIL RTX Mailbox example

Hi,

i'm currently experimenting with RTX Mailboxes and i tried one the Keil example which is not working. I stripped some unimportant things like serial initialization, etc

OS_TID tsk1;                          /* assigned identification for task 1  */
OS_TID tsk2;                          /* assigned identification for task 2  */

typedef struct {                      /* Message object structure            */
  float voltage;                      /* AD result of measured voltage       */
  float current;                      /* AD result of measured current       */
  U32   counter;                      /* A counter value                     */
} T_MEAS;

os_mbx_declare (MsgBox,16);           /* Declare an RTX mailbox              */
_declare_box (mpool,sizeof(T_MEAS),16);/* Dynamic memory pool                */

__task void send_task (void);
__task void rec_task (void);

/*----------------------------------------------------------------------------
 *  Task 1:  RTX Kernel starts this task with os_sys_init (send_task)
 *---------------------------------------------------------------------------*/
__task void send_task (void) {
  T_MEAS *mptr;

  tsk1 = os_tsk_self ();              /* get own task identification number  */
  tsk2 = os_tsk_create (rec_task, 0); /* start task 2                        */
  os_mbx_init (MsgBox, sizeof(MsgBox));/* initialize the mailbox             */
  os_dly_wait (5);                    /* Startup delay for MCB21xx           */

  mptr = _alloc_box (mpool);          /* Allocate a memory for the message   */
  mptr->voltage = 223.72;             /* Set the message content             */
  mptr->current = 17.54;
  mptr->counter = 120786;
  os_mbx_send (MsgBox, mptr, 0xffff); /* Send the message to the mailbox     */
  IOSET1 = 0x10000;
  os_dly_wait (100);

  mptr = _alloc_box (mpool);
  mptr->voltage = 227.23;             /* Prepare a 2nd message               */
  mptr->current = 12.41;
  mptr->counter = 170823;
  os_mbx_send (MsgBox, mptr, 0xffff); /* And send it.                        */
  os_tsk_pass ();                     /* Cooperative multitasking            */
  IOSET1 = 0x20000;
  os_dly_wait (100);

  mptr = _alloc_box (mpool);
  mptr->voltage = 229.44;             /* Prepare a 3rd message               */
  mptr->current = 11.89;
  mptr->counter = 237178;
  os_mbx_send (MsgBox, mptr, 0xffff); /* And send it.                        */
  IOSET1 = 0x40000;
  os_dly_wait (100);

  os_tsk_delete_self ();              /* We are done here, delete this task  */
}

/*----------------------------------------------------------------------------
 *  Task 2: RTX Kernel starts this task with os_tsk_create (rec_task, 0)
 *---------------------------------------------------------------------------*/
__task void rec_task (void) {
  T_MEAS *rptr;

  for (;;) {
    os_mbx_wait (MsgBox, (void **)&rptr, 0xffff); /* wait for the message    */
    printf ("\nVoltage: %.2f V\n",rptr->voltage);
    printf ("Current: %.2f A\n",rptr->current);
    printf ("Number of cycles: %d\n",rptr->counter);
    _free_box (mpool, rptr);           /* free memory allocated for message  */
  }
}


/*----------------------------------------------------------------------------
 *        Main: Initialize and start RTX Kernel
 *---------------------------------------------------------------------------*/
int main (void) {                     /* program execution starts here       */


  _init_box (mpool, sizeof(mpool),    /* initialize the 'mpool' memory for   */
              sizeof(T_MEAS));        /* the membox dynamic allocation       */
  os_sys_init (send_task);            /* initialize and start task 1         */
}

i get the error: main.cpp(131): error: #513: a value of type "void *" cannot be assigned to an entity of type "T_MEAS *" at this line:

mptr = _alloc_box (mpool);          /* Allocate a memory for the message   */

Does anyone have an idea how this should be used?