Puzzle
A bug that crops up time and time again:

class BuggyInterface
{
public:
virtual void interfaceMethod();
}

class ImplementsBuggyInterface: public BuggyInterface
{
public:
ImplementsBuggyInterface();
~ImplementsBuggyInterface();
void interfaceMethod();
}

BuggyInterface* p = new ImplementsBuggyInterface();
delete p;


Guess what's wrong!