Prohibit Copy Constructor in C++ – Most Reliable Methods

Sometimes it's necessary to prohibit a copy constructor in a C++ class so that class becomes "non-copyable". Of course, operator= should be prohibited at the same time.

So far I've seen two ways to do that. Way 1 is to declare the method private and give it no implementation:

class Class {
//useful stuff, then
private:
    Class( const Class& ); //not implemented anywhere
    void operator=( const Class& ); //not implemented anywhere
};

Way 2 is to declare the method private and give it "empty" implementation:

class Class {
//useful stuff, then
private:
    Class( const Class& ) {}
    void operator=( const Class& ) {}
};

IMO the first one is better – even if there's some unexpected reason that leads to the copy constructor being called from the same class member function there'll be a linker error later on. In the second case this scenario will be left unnoticed until the runtime.

Are there any serious drawbacks in the first method? What's a better way if any and why?