Re: [boost] [review] Review of Boost.Exception

From: Emil Dotchevski (emildotchevski_at_[hidden])
Date: 2007-09-30 15:02:59

> get_error_info(T const &) returns a pointer instead of a const copy of
> the actual error_info it gets. This can be a potential headache to
> deal with especially in examining the error_info associated with the
> thrown exception. A proposed change would be to have get_error_info(T
> const &) return a const copy of the data, while get_error_info_ptr(T
> const &) would return a pointer as in the current version.

I suppose the behavior you propose for get_error_info is to throw an
exception if the requested data is not available in the exception. But
think about the situation you're describing: you catch an exception,
and now you want to query it for error_info -- what good does it do
for that context to throw an exception?

Sure, there are use cases when you know an error_info must be present
in the exception or you have a bug, but in that case it makes more
sense to assert on get_error_info.

> Although it might also take quite some effort to remove the runtime
> polymorphic behavior which relies on shared_ptr<>'s and virtual tables
> with info_base <snipped>

I never had any performance-related issues with this library, and I've
been using it for more than a year now. Until we have evidence that we
need to optimize, I would prefer to keep the implementation as simple
as possible.

> My concern with the use of shared_ptr<>'s is that in cases where an
> exception pertaining to "out of memory" conditions would arise,
> throwing a boost::exception and then having to allocate more memory
> just to encapsulate additional information would lead to undesirable
> termination.

Could you elaborate a bit more? Can you come up with a theoretical
example that demonstrates your concerns?

Thanks for you feedback!

Emil Dotchevski