[boost] Re: [bug]: optional<T> fails on self-assignment

From: David Abrahams (dave_at_[hidden])
Date: 2005-02-16 09:36:09

"Peter Dimov" <pdimov_at_[hidden]> writes:

> David Abrahams wrote:
>> "Joe Gottman" <jgottman_at_[hidden]> writes:
>>
>>>
>>>    I disagree.  This may ensure the basic exception-safety
>>> guarantee, but most code that uses optional<T> will use
>>> T::operator=() at some point or other.  So if T::operator=() is not
>>> exception-safe
>>
>> Whoa, here we go again!  You seem to be assuming
>>
>>  basic exception-safety guarantee == "not exception-safe."
>>
>> That's just not true for any reasonable definition of
>> "exception-safe."
>
> No, he isn't assuming that. "Not exception safe" == "does not provide basic" 
> in the above paragraph. Fernando's goal, IIUC, was to make 
> optional<T>::operator= provide the basic guarantee even when T::operator= 
> does not. We are arguing that this is not necessary 

Agreed.  There's no good reason to try to "fix" broken classes.

> and that optional<T>::operator= should just mirror the exception
> safety guarantee of T::operator= and T::T( T const & ).

Sounds fine to me.

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com