Re: [boost] Boost Exception and support for cloning

From: Josh Napoli (jnapoli_at_[hidden])
Date: 2007-10-23 00:44:37

> This can be done by adding a clone() virtual function to
boost::exception.

Since the clone function is just a stopgap until 0x, would it be better
to implement it without explicitly adding the clone function to the
interface? For example, use an auto-registration idiom to collect all of
the exception types:
  void throw_exception(const E&e) {
    static autoregister_exception<E> registration;
    throw e;
  }

Provide an implementation of "copy_exception" that searches for a
type_info match. Perhaps this clumsy implementation is better than
everyone ending up a few years from now with dependencies on an obsolete
clone interface.

> Why not throw a std::ostringstream directly then? :)

I was just trying to demonstrate that:
- Tagged fields could be mixed with untagged fields to encourage more
ad-hoc data in the exception (to aid debugging).
- Both untagged and tagged types can be visited by the error handler in
a type-safe manner. Tagging is only really required when the identity of
the field would otherwise be ambiguous.
- Fields from one exception object could be copied into a second.
- Formatting of the "what" message can be specified inline at the throw
site but remain uninterpreted until the error handler is reached.

-Joshua Napoli