C++: Throwing an exception invokes the copy constructor?

Question

We have an custom error class that is used whenever we throw an exception:

class AFX_CLASS_EXPORT CCLAError : public CObject

It has the fol

Answer 1

Several points:

1st of all don't call throw new foo() use throw foo

2nd when your write:

catch(foo const &e) {
   throw e;
}

You actually create a new exception, and if for example the exception that was thrown is subclass of foo they my calling throw e you would loose this information and actually use a copy constructor to generate foo from e - whatever it was.

Now when you call

catch(foo const &e) {
   throw;
}

You don't create a new exception but rather propagate the same exception.

So: never use throw e; to propagate the exception forward, use throw;