hello and farewell pthread

gistfile1.c

/* 
   pthtest --- hello pthread.
 
   gcc -pthread -o pthtest pthtest.c
*/
#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>


typedef struct data_{
  int vala;
  int valb;
} data ;

void *thread_a( void *dat);
void *thread_b( void *dat);

int main(int argc, char** argv) {
  
  int ret;
  data datX;
  pthread_t threadA, threadB;
  pthread_attr_t attr;
  
  datX.vala = 0;
  datX.valb = 0;
  pthread_create (&threadA, NULL, thread_a, (void*)&datX );
  pthread_create (&threadB, NULL, thread_b, (void*)&datX );

  while(1){
    fprintf(stderr, "\ra(id %d) is %18d, b(id %d) is %18d", 
            threadA, datX.vala, threadB, datX.valb);
    fflush(stderr);
    usleep(250);
  }
  exit(0);
}

void *thread_a(void *dat){
  data* ptr;
  ptr = (data*)dat;
  while(1){
    ptr-> vala = ptr->vala +1;
  }
  return;
}

void *thread_b(void *dat){
  data* ptr;
  ptr = (data*)dat;
  while(1){
    ptr-> valb = ptr->valb +2;
  }
  return;
}