Re: [boost] [variant2] Andrzej's review

Subject: Re: [boost] [variant2] Andrzej's review
From: Rainer Deyke (rainerd_at_[hidden])
Date: 2019-04-14 16:32:27

On 13.04.19 17:33, Peter Dimov via Boost wrote:
> First off, the basic guarantee isn't worse than useless, it's the 
> minimum standard that every non-broken component must meet, and everyone 
> who argues otherwise isn't worth listening to.

I would say that the absolute minimum requirement is that all objects 
are left destructible.  It is not a requirement that all possible 
operations on an object remain defined behavior - and there is plenty of 
precedent for certain operations not being allowed on certain objects 
even in the absence of exceptions.  A variant without the never-empty 
guarantee can meet that requirement, even if the empty state is an 
exceptional state that can only be entered through an exception.  There 
may be valid arguments for a never-empty variant, but it is possible to 
write correct code that recovers from exceptions even with an 
exceptional-empty variant.

I'm not arguing against the basic exception guarantee per se.  I am 
arguing for an interpretation of the basic guarantee that allows for 
exceptional states.

-- 
Rainer Deyke (rainerd_at_[hidden])