Fibonacci sequence with generating function

#include <stdio.h>
#include <stdbool.h>

unsigned fibonacci(bool reset) {
    static unsigned n1 = 0;
    static unsigned n2 = 1;

    if(reset) {
        n1 = 0;
        n2 = 1;
    }

    unsigned retval = n1;

    n2 += n1;
    n1 = n2 - n1;

    return retval;
}

int main() {
    for(size_t i = 0; i < 20; ++i) {
        if(i == 10) printf("\n-- reiniciando --\n");
        printf("%u\n", fibonacci(i == 10));
    }
}