error occured when using function sem_init - c

Question

I'm using Linux to learn semaphore, trnna test the function sem_init. The code seems simple but the error is unexpected, don't know why. Here's the code and the errors is below the code.
#include <stdio.h>
#include <pthread.h>
#include <semaphore.h>
#include<unistd.h>
#include <stdlib.h>
#define NITER 1000000
int cnt = 0;
sem_t mutex;
sem_init(&mutex,0,1);
void * Count(void * a)
{
int i, tmp;
for(i = 0; i < NITER; i++)
{
sem_wait(&mutex);
tmp = cnt; /* copy the global cnt locally */
tmp = tmp+1; /* increment the local copy */
cnt = tmp; /* store the local value into the global cnt */
sem_post(&mutex);
}
}
int main(int argc, char * argv[])
{
pthread_t tid1, tid2;
if(pthread_create(&tid1, NULL, Count, NULL))
{
printf("\n ERROR creating thread 1");
exit(1);
}
if(pthread_create(&tid2, NULL, Count, NULL))
{
printf("\n ERROR creating thread 2");
exit(1);
}
if(pthread_join(tid1, NULL)) /* wait for the thread 1 to finish */
{
printf("\n ERROR joining thread");
exit(1);
}
if(pthread_join(tid2, NULL)) /* wait for the thread 2 to finish */
{
printf("\n ERROR joining thread");
exit(1);
}
if (cnt < 2 * NITER)
printf("\n BOOM! cnt is [%d], should be %d\n", cnt, 2*NITER);
else
printf("\n OK! cnt is [%d]\n", cnt);
pthread_exit(NULL);
}
my english is bad, if anything is hard to understand please tell me and ill respond you as soon as possible!thx

Answer 1

You can declare variables outside the main and the other function which mean that the variable is global .
But to call the function sem_init(&mutex,0,1); you should do it from the main or from another function. In your case , you have to do it in the main.
After moving the sem_init inside the main it compile
nabil#DESKTOP-8ECTID4:~/stackoverflow$ gcc bad.c -o bad -lpthread
nabil#DESKTOP-8ECTID4:~/stackoverflow$