How do I convert a 64bit integer to a char array and back?

Question

I am having trouble converting a int64_t to a char array and back. I don\'t know what is wrong with the code below, it makes complete logical sense to me. The code works for

Answer 1

void int64ToChar(char mesg[], int64_t num) {
    *(int64_t *)mesg = num; //or *(int64_t *)mesg = htonl(num);

}