template function instantiation

[George2]

Hello everyone,


For the following code from Bjarne's book, it is stated that template parameter T for function g will be instantised as int other than double. My question is why there are not two instantiations for both int and double version of template function g?

// section C.13.8.3 Point of Instantiatant Binding

template <class T> void f (T a) { g(a); }

void g(int);

void h()
{
	extern g (double);
	f (2);
}

Here is the related statement from Bjarne,

--------------------
Each use of a template for a given set of template arguments defines a point of instantiation.
That point is the nearest global or namespace scope enclosing its use,
just before the declaration that contains that use.
--------------------

Does it before g (double) is not global function or namespace scope enclosing its use? If yes, I do not know why g (double) is not a global function, since it is declared as extern and some other compile unit should expose it?


thanks in advance,
George