RAII just uses c++ constructors, destructors and lifetime rules to automatically do one thing when an object is constructed on the stack, and automatically do a

RAII just uses c++ constructors, destructors and lifetime rules to automatically do one thing when an object is constructed on the stack, and automatically do another thing when control leaves the scope in which the object exists. The second part (the destructor) is key, because it will be executed whether control leaves 'normally' or because an exception was thrown.