In which case a function / method is guarantee not to throw an exception ?

I want to understand if sometime it is possible to be sure
a function / method will never throw an exception;

I think a function / method that only perform assignment / copy
operation on primitive types like int, bool, double etc., then
it is guarantee it will never throw an exception
so it can be qualified with "throw()"

(Note: just at this very beginning, I do not want to ask
if it is a good practice such a qualifying, just suppose
it is already present in some old library)

But I wonder if a class containing basic type (or also
other class containing basic types) can be manipulated
and the function / method can still offering a no-throw guarantee;

an example:

// a class of only basic types
class A {

 int i;
 double j;
 bool k;

public:
 A() : i(0), j(0), k(0) {};

 A( int I, doule J, bool K ) : i(I), j(J), k(K) {};
 };

// a function that call constructor,
// copy constructor, copy operator and
// create a temporary object A
 A afunction( int i, double j, bool k) throw()
 {
    A a( i, j, k);

    A b= a;

    A c;

    c= b;

    return( A( i, j ,k) );
 }

It will be correct the fun. afunction() will never throw ? or I am
missing
some fundamental point ?

thanks
Giaffy