Simple pthread prog: segmentation fault

Trying to see how pthread works by running a simple program but I am getting segmentation fault (core dumped) at pthread_create

#include <stdio.h>
#include <pthread.h>
#include <stdlib.h>

void* testfunc(void* arg) {
  while (1) {
    printf("testfunc");
  }
}

int main(void) {
  printf("helo\n");

  if (pthread_create(NULL, NULL, &testfunc, NULL) != 0) {
    perror("pthread failed to create\n");
  }

  while (1) {
    printf("main function\n");
    sleep(1000);
  } 

  return 0;
}

What seems to be causing the problem? I am on Ubuntu 20.04 if that matters.

>Solution :

You can’t pass NULL for pthread_create‘s first argument.

Before returning, a successful call to pthread_create() stores the ID of the new thread in the buffer pointed to by thread

Also, pthread_create doesn’t set errno, so using perror makes no sense, at least not without some prep.

on error, it returns an error number, and the contents of *thread are undefined.

Fixed:

pthread_t thread;
if ( ( errno = pthread_create(&thread, NULL, &testfunc, NULL) ) != 0 ) {
    perror("pthread failed to create\n");
}

...

pthread_join(thread);  // Normally.