Problems in creating libraries

[Riccardo 'Taro']

Hi there! I got a strange error when i was trying to create a library with a function that execute a bubble-sort. The error is this:
" undefined reference to 'bubblesort'
collect2.exe: error: ld returned 1 exit status "
I leave the codes of the .h .c and main.c files below.
I think i'm one of the few who got this error-code. If someone here can help me i would be really glad. Thanks!

extern void bubblesort (int, int[])

#include "bbsort.h"

void bubblesort (int n, int a[]) {
    int i, j, temp;
    for (i=0; i<n-1; i++)
        for (j=0; j<n-1; j++)
            if (a[j]>a[j+1]) {
                temp=a[j];
                a[j]=a[j+1];
                a[j+1]=temp;
            }
}

#include "bbsort.h"
#include <stdio.h>
#define n 8

int main () {
    int a[n];
    
    printf ("insert values in the arrey:\n\t");     //load the arrey
    for (int i=0; i<n; i++) {
        scanf("%d", &a[i]);
        printf ("\t");
    }

    bubblesort(n, a);                         //bubblesort instruction

    for (int i=0; i<n; i++) {                //print the sorted arrey
        printf ("%d\t", a[i]);
    }

    return 0;
}