FAQ 35.13 How do CORBA exceptions compare to C exceptions?

FAQ 35.13 How do CORBA exceptions compare to C++ exceptions?

The same but different.

At first glance, it appears that C++ exceptions and CORBA/IDL exceptions are pretty much the same. For example the semantics of instantiating, throwing, and catching exceptions are the same as with C++. But there are also differences, some minor and some major.

As a minor difference, C++ implementations of CORBA member functions need to include CORBA::SystemException in the exception specification (either that or not have an exception specification; see FAQ 9.04). Another minor difference is that each CORBA exception must be mapped to a C++ class that inherits from the abstract base class CORBA::UserException.

A major difference is that normal C++ exceptions have both state and behavior but CORBA/IDL exceptions cannot have behavior. This is because exceptions may get transmitted to different computers (e.g., when the thrower and the catcher are on different computers), and it's easier for the implementation to copy pure data objects than to copy objects that have behavior.

IDL does not support inheritance in exception declarations, which can get quite nasty when C++ exceptions are mapped to CORBA exceptions and then thrown around the ORB. Finally, memory management is tough enough with C++ exceptions, but the issues become substantially more complex in a distributed object environment.

So don't be lulled into a false sense of security because the words sound the same. Exceptions in CORBA require a great deal of knowledge and experience that the beginner does not have and does not gain easily, no matter how familiar they are with C++ exceptions.