Re: [boost] [optional] problems with swap()

From: Niels Dekker - mail address until 2008-12-31 (nd_mail_address_valid_until_2008-12-31_at_[hidden])
Date: 2008-04-10 16:56:41

Thorsten Ottosen wrote:
> No user expects swap to throw or invalidate iterators or references like
> the current implementation does.

I do agree that it's a pity that the current implementation of
optional::swap might throw an exception.  Still, like Andrey Semashev,
I'd rather not have it require T to be default constructible.  Because I
can imagine that people typically use optional<T> for a
non-DefaultConstructible T.  (A nice thing about boost::optional<T> is
that it provides a default constructor, even for those types T that
don't have one.)

What would you think of having boost::optional implemented by holding a
pointer to T, instead of an aligned_storage object and a m_initialized
flag?  It would manage the memory that the pointer would point to. 
Having NULL would indicate being uninitialized. (I admit it's a rather
theoretical question, because I don't even know if Fernando would like
such an approach...)

Kind regards,
-- 
Niels Dekker
http://www.xs4all.nl/~nd/dekkerware
Scientific programmer at LKEB, Leiden University Medical Center