sem_unlink(): permission denied on macOS - c

Question

I am working on a school assignment using semaphores, every time I restart my mechine everything works as expected but after running my code, the second try gives undefined results. I've come to a conclusion that my machine don't give me permission to unlink any created semaphores, and checking the errno showed that my conclusion was correct. It gives errno EACCES, how can I fix this problem? I am working on the last visions of Xcode (12.2).
The code I am running:
#include <stdlib.h>
#include <unistd.h>
#include <pthread.h>
#include <semaphore.h>
#include <fcntl.h> /* For O_* constants */
#include <errno.h>
const char *semName1 = "my_sema1";
const char *semName2 = "my_sema2";
int main(int argc, char **argv)
{
pid_t pid;
sem_t *sem_id1 = sem_open(semName1, O_CREAT, O_RDWR, 1);
sem_t *sem_id2 = sem_open(semName2, O_CREAT, O_RDWR, 0);
int i, status;
pid = fork();
if (pid) {
for (i = 0; i < 100; i++) {
sem_wait(sem_id1);
putchar('A'); fflush(stdout);
sem_post(sem_id2);
}
sem_close(sem_id1);
sem_close(sem_id2);
wait(&status);
int error = sem_unlink(semName1);
int hej2 = sem_unlink(semName2);
printf("%d \n",error);
if (errno == EACCES){
printf("%d \n",error);
}
} else {
for (i = 0; i < 100; i++) {
sem_wait(sem_id2);
putchar('B'); fflush(stdout);
sem_post(sem_id1);
}
sem_close(sem_id1);
sem_close(sem_id2);
}
}
Appreciate your help

Answer 1

Quick Answer: Run the program as root
Long Answer:
Given this code snippet:
#include <errno.h>
#include <semaphore.h>
#include <stdio.h>
#include <stdlib.h>
int main(void)
{
sem_t *sem_id1 = sem_open("sem_id1", O_CREAT, O_RDWR, 0);
if (sem_id1 == SEM_FAILED)
{
perror("sem_open");
exit(1);
}
printf("sem_open: Successful\n");
int rc = sem_unlink("sem_id1");
if (rc != 0)
{
perror("sem_unlink");
exit(1);
}
printf("sem_unlink: Successful\n");
return 0;
}
The first time it's run, it will let you create the semaphore, but fail to unlink it:
./main
sem_open: Successful
sem_unlink: Permission denied
The second time it will fail even to create the semaphore:
./main
sem_open: Permission denied
The issue is clearly with permissions, and running the program as root fixes it:
sudo ./main
sem_open: Successful
sem_unlink: Successful
Why does it need root privileges?
Quoting from the man page:
POSIX semaphores come in two forms: named semaphores and unnamed semaphores.
...
Persistence
POSIX named semaphores have kernel persistence: if not removed by sem_unlink(3), a semaphore will exist until the system is shut down.
These are named semaphores.
The fn sem_open and sem_unlink are possibly affecting processes that don't belong to you: imagine if you could run a program that overwrites or removes another process' semaphore without root permissions!