Peter,
According to the specification (14.7.1.5), the requirement of that
template instantiation is left up to the implementation.
--
If the overload resolution process can determine the correct function
to call without instantiating a class
template definition, it is unspecified whether that instantiation
actually takes place. [Example:
template <class T> struct S {
operator int();
};
void f(int);
void f(S<int>&);
void f(S<float>);
void g(S<int>& sr) {
f(sr); //instantiation of S<int> allowed but not required
// instantiation of S<float> allowed but not required
};
âend example]
corey
On Tue, 1 Feb 2005 22:02:15 +0100, Peter Soetens
<peter.soetens@xxxxxxxxxxxxxxxxxxx> wrote:
> Hi,
>
> The code below compiles fine with Intel's icc. However,
> all gcc versions refused to compile it saying :
>
> g++ -c -o ttt.o ttt.cpp
> ttt.cpp: In instantiation of `Property<F>':
> ttt.cpp:15: instantiated from `bool Property<T>::change(PropOp*) [with T =
> double]'
> ttt.cpp:23: instantiated from here
> ttt.cpp:13: error: `Property<T>::val' has incomplete type
> ttt.cpp:1: error: forward declaration of `struct F'
>
> -----Code-----
> struct F;
>
> template< class T >
> struct Property;
>
> struct PropOp {
> bool update( Property<F>* f) { return false; }
> bool update( Property<double>* d) { return true; }
> };
>
> template<class T>
> struct Property {
> T val;
> bool change( PropOp* p) {
> return p->update( this ); // Line 15
> }
> };
>
> int main()
> {
> PropOp po;
> Property<double> pd; // Line 23
> pd.change( &po );
> return 0;
> }
>
> ----EndCode---
>
> May I submit this as a bug ? I believe Property<F> should not be instantiated
> in line 15, only Property<double> should be.
>
> Peter
>
> PS: Please CC me.
>
> --
> ------------------------------------------------------------------------
> Peter Soetens, Research Assistant http://www.orocos.org
> Katholieke Universiteit Leuven
> Division Production Engineering, tel. +32 16 322773
> Machine Design and Automation fax. +32 16 322987
> Celestijnenlaan 300B peter.soetens@xxxxxxxxxxxxxxxxxxx
> B-3001 Leuven Belgium http://www.mech.kuleuven.ac.be/pma
> ------------------------------------------------------------------------
>
