Test if PDEATHSIG is sent to child processes on thread exit in FreeBSD and Linux

proc_test_freebsd.c

#include <sys/procctl.h>
#include <stdio.h>
#include <err.h>
#include <unistd.h>
#include <stdlib.h>
#include <signal.h>
#include <pthread.h>

void child_handler(int signal) {
  printf("Child got signal: %d\n", signal);
  exit(signal);
}

void *startChild(void *data) {
  pid_t pid;
  fflush(stdout);
  switch (pid = fork()) {
    case -1:
      err(1, "Failed to fork");
    case 0:
      signal(SIGHUP, child_handler);
      int signal = SIGHUP;
      int errno = procctl(P_PID, pid, PROC_PDEATHSIG_CTL, &signal);
      printf("Hello from child process!\n");
      char buf[10];
      read(0, buf, 10);
      exit(0);
    default:
      break;
  }
  sleep(1);
  return 0;
}

int main() {
  pthread_t t;
  pthread_create(&t, 0, *startChild, 0);

  pthread_join(t, 0);
  printf("Hello from parent process!\n");
  sleep(5);
  printf("Goodbye from parent process!\n");
  return 0;
}

/*
Prints:

Hello from child process!
Hello from parent process!
Goodbye from parent process!
Child got signal: 1
*/

proc_test_linux.c

#include <sys/prctl.h>
#include <stdio.h>
#include <err.h>
#include <unistd.h>
#include <stdlib.h>
#include <signal.h>
#include <pthread.h>

void child_handler(int signal) {
  printf("Child got signal: %d\n", signal);
  exit(signal);
}

void *startChild(void *data) {
  pid_t pid;
  fflush(stdout);
  switch (pid = fork()) {
    case -1:
      err(1, "Failed to fork");
    case 0:
      signal(SIGHUP, child_handler);
      int errno = prctl(PR_SET_PDEATHSIG, SIGHUP);
      printf("Hello from child process!\n");
      char buf[10];
      read(0, buf, 10);
      exit(0);
    default:
      break;
  }
  sleep(1);
  return 0;
}

int main() {
  pthread_t t;
  pthread_create(&t, 0, *startChild, 0);

  pthread_join(t, 0);
  printf("Hello from parent process!\n");
  sleep(5);
  printf("Goodbye from parent process!\n");
  return 0;
}

/*
Prints:

Hello from child process!
Hello from parent process!
Child got signal: 1
Goodbye from parent process!
*/