Puzzle: To avoid type checking

Question

I formed a good interview question by accident. :)

template<typename T> bool foo (T obj) { if(typeid(T) == typeid(obj)) return false; return true; // <-- execute this } 

You should call (only above) foo() so that it returns true . Conditions:

• Cannot edit or reload foo() or typeid
• Allowed to use specific platform hackers
• No #define allowed

Answer 1

 int main () { typedef char C[1]; foo<C>(0); // returns true; } 

Refer to this question for an explanation of this answer and the root of this question.

Answer 2

 #include <cassert> struct B { virtual ~B() {} }; int main() { struct : B {} x; assert(foo<B&>(x)); } 

The action is there .