fizzBuzz.c

char** fizzBuzz(int n, int* returnSize) {
    struct _ {
        char *rets[n + 1];
        char data[0];
    } * ret = calloc(sizeof(struct _) + n * 9 + 1, sizeof(char));
    *returnSize = n;
    
    char * sp = ret->data;
    for (int i = 1; i <= n; ++i, sp += 9) {
        ret->rets[i - 1] = sp;
        (i % 5 && i % 3)
            ? sprintf(sp, "%d", i)
            : sprintf(sp, "%s%s", (i % 3)
                                      ? ""
                                      : "Fizz",
                                  (i % 5)
                                      ? ""
                                      : "Buzz");
    }
    ret->rets[n] = sp;
    return ret->rets;
}

main.c

int main(int argc, char *argv[])
{
    int size;
    char **ret = fizzBuzz(15, &size);
    for (char **p = ret; **p; ++p)
        printf("%s\n", *p);
    return 0;
}