Adding to G++: Adding a warning on throwing unspecified exceptions.

Brendon Costa bcosta@avdat.com.au
Thu Sep 25 22:19:00 GMT 2008


Simon Hill wrote:
> Brendon Costa said:
>> The author of the template class or container can't know
>> what types of exceptions will be thrown from them, so you must define
>> them as being able to throw all exceptions (which is how they are
>> currently).
> Ouch, you have a point. But couldn't you put this round the other way.
> Place the onus on the user of the template to comply with the
> exception guarantees inside the template. Unfortunately that would
> likely cause problems with some existing code.
>
> ...
>
> In other words, would you gain more from a tight exception
> specification than you'd lose by not being able to do this?
>
You as an author of a new template class "could" define it the other way.

The issue here is that doing so restricts usage of the generic
component. In specific cases this may be desirable, but not for generic
components like STL containers or those in boost. For generic components
you want to make them as useful as possible. Even if at the time of
writing the container you do not foresee that throwing any type of
exception is a good idea, users may come up with some way of using it
that you just never thought about.

I.e. I think the general philosophy is to define only what restrictions
are necessary to implement the template, not necessarily what we think
constitute good uses of the template at the time we created it.


Brendon.



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