In Solaris, gcc gives me

implicit declaration of function `getopt'

when compiling

#include <unistd.h>
#include <stdlib.h>

int main(int argc, char *argv[]) {
    getopt(1,argv,"");
    return 0;
}

The man page for getopt says something about including unistd.h or stdio.h, however even though I'm inluding both I still get this warning. Is this normal? Is using functions that aren't explicitly declared common in Unix development?