Re: [boost] Another variant type (was: [peer review queue tardiness] [was Cleaning out the Boost review queue] Review Queue mem

Subject: Re: [boost] Another variant type (was: [peer review queue tardiness] [was Cleaning out the Boost review queue] Review Queue mem
From: Eric Niebler (eniebler_at_[hidden])
Date: 2015-04-04 20:55:24

On 4/4/2015 4:42 PM, Larry Evans wrote:
> On 04/04/2015 06:25 PM, Steven Watanabe wrote:
>> AMDG
>> 
>> On 04/04/2015 05:20 PM, Larry Evans wrote:
>>> On 04/04/2015 06:18 PM, Steven Watanabe wrote:
>>>> The reason that aligned storage doesn't work has nothing to
>>>> do with calculating the alignment.
>>> 
>>> Why does using aligned_storage not work, please?
>>> 
>> 
>> On 04/04/2015 04:06 PM, Matt Calabrese wrote:
>>> You need to use a recursive union if you are to get some
>>> constexpr support.
>> 
> OK.  So Matt, could you please elaborate on why constexpr support
> requires a recursive union?

To put an object into aligned storage requires placement new, which is
not constexpr. Using a recursive union avoids the need for placement new.

-- 
Eric Niebler
Boost.org
http://www.boost.org