Cancelation Points

#include<stdio.h>
#include<unistd.h>
#include<pthread.h>
#include<stdlib.h>
  
void clean(void *buf)
{
    puts("cleaning");
    free(buf);
}
  
void *threadfn1(void *p)
{
    void *pbuf;
    pbuf=malloc(1000);
    if(pbuf!=NULL)
    {
        pthread_cleanup_push(clean,pbuf);
        puts("thread 1 start");
        sleep(7);
        puts("thread 1 end");
        pthread_cleanup_pop(1);
    }
    return NULL;
}
  
void *threadfn2(void *p)
{
    int x;
    int o_state;
    pthread_setcancelstate(PTHREAD_CANCEL_DISABLE,&o_state);
  
    for(x=0;x<5;x++)
    {
        puts("hello");
    }
  
    pthread_setcancelstate(o_state,&o_state);
  
    return NULL;
}
  
int main()
{
    pthread_t t1;
    pthread_create(&t1,NULL,threadfn1,NULL);
    sleep(5);
    pthread_cancel(t1);
    printf("end test\n");
    sleep(50);
    return 0;
}