AMDG "Richard Crossley" wrote:

Thanks for your help, though I'm somewhat uncertain as to what's going on. Your example would appear to be able to be simplified further or am I misunderstanding?

struct undefined;

template<class T> struct C { T t; };

void f(void*){}

int main() { C<undefined> * p = 0; // OK f(p); // ERROR }

You're right. I just got confused. I must have tried something like template<class T> struct C { //no use of T here }; I think what the compiler is doing may actually be correct. (see 3.4.2 and 14.7.1). The standard was obviously not written with placeholders in mind. Actually there is an easy hack to make this work. Just add: struct boost::recursive_variant_ {}; In Christ, Steven Watanabe