#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <sys/ptrace.h>
#include <sys/types.h>
#include <pthread.h>

static int thread_res = 0;

int test_ptrace(pid_t p)
{
  int res;
  printf("thread is %d\n", getpid());

  printf("%d wants to ptrace %d\n", getpid(),  p);
  res = ptrace(PTRACE_ATTACH, p, NULL, NULL);
  if (res == 0) {
    res = ptrace(PTRACE_KILL, p, NULL, NULL);
  }

  return res;
}

static void * test_ptrace_start(void * args){
  pid_t p = *(pid_t *)args;
  thread_res = test_ptrace(p);

  pthread_exit((void *)&thread_res);
}

int main(int argc, char *argv[])
{
  const int ptrace_from_thread = 1;
  pthread_t thread;
  int res;

  pid_t p = fork();
  switch (p) {
  case -1:
    exit(1);
    break;

  case 0:
    /* Child */
    printf("child is %d\n", getpid());
    sleep(100);
    exit(0);
    break;

  default:
    /* Parent */
    printf("parent is %d\n", getpid());
    break;
  }

  if (ptrace_from_thread > 0) {
    pthread_create(&thread, NULL, test_ptrace_start, (void *)&p);
    pthread_join(thread, NULL);
    res = thread_res;
  } else {
    res = test_ptrace(p);
  }

  if (res == 0) {
    printf("ptrace of %d successful\n", p);
  } else {
    printf("ptrace of %d failed\n", p);
  }

  exit(0);
}