Forward declaration of class used in template function is not compiled by clang++

Question

There is this code:

class A;

template 
void fun() {
   A a;
}

class A { 
public: 
   A() {  } 
};

int main() { 
   fun(); 
   return         


        

Answer 1

Clang is correct, as far as I know. At your function fun, you do not know the size of A, and since your allocating an A, you need to know it's size. In my opinion, gcc is way to forgiving here.