Re: [boost] [variant] Heads-up!

Subject: Re: [boost] [variant] Heads-up!
From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2019-04-29 17:44:08

AMDG

On 4/29/19 11:30 AM, Antony Polukhin via Boost wrote:
>
> I've merged a very cool optimization by Nikita Kniazev into the master
> branch. From now on boost::variant does pointer stealing for recursive
> variants.
> 
> This significantly improves the performance of the variants move constructors.
> 
> However if you use a variant variable after the std::move for anything
> except destruction and assignment then you're getting an UB. Beware!
> 

boost::variant goes to great lengths to prevent
exactly this situation.  You just broke it.  This
change is unacceptable.  Please revert it.  This
optimization can be used iff. you have a way to
construct a valid object in the rhs.

In Christ,
Steven Watanabe