TITLE: templates and incomplete types


PROBLEM: clgonsal@undergrad.math.uwaterloo.ca (Carl Laurence Gonsalves)

I'm trying to do something like this:

template< class T >
class Foo{
    bar( T& t ){
	T		*val;
	// stuff...
	val = new T( t );
	// stuff...
    }
};

Basically, I'm trying to use the copy constructor of "T". I tried compiling
this with GCC and it said:

"Invalid use of undefined type 'struct T'."


RESPONSE: clamage@Eng.Sun.COM (Steve Clamage), 21 Aug 95

The code you show is valid. When you intantiate the template, however,
you must use a complete type. If you did something along these lines
	struct X;
	Foo<X> f0; // incomplete type X
	Foo<Y> f1; // unknown type Y
it could possibly cause such an error message.

If you did instantiate Foo with a defined type, it might be a compiler
bug -- see if you have the latest version of gcc.