Exception slicing - is this due to generated copy constructor?

Question

I\'ve just fixed a very subtle bug in our code, caused by slicing of an exception, and I now want to make sure I understand exactly what was happening.

Here\'s our b

Answer 1

Yes.

throw e;

throws an exception of the static type of e, regardless of whatever e actually is. In this case, the Derived exception is copied to an Exception using a copy constructor.

In this case you can just

throw;

to get the Derived exception bubble up correctly.

If you're interesting in polymorphical throwing in some other cases, refer to the always so useful C++ FAQ Lite.