Re: [boost] [config] RFC PR 82

Subject: Re: [boost] [config] RFC PR 82
From: Andrey Semashev (andrey.semashev_at_[hidden])
Date: 2015-12-01 09:59:11

On 2015-12-01 17:18, Agustín K-ballo Bergé wrote:
>
> But what tops it all, what makes this decision a plain and simple
> mistake, is that this "just works" because implementations map this kind
> of undefined behavior into specific well-defined behavior. So it's just
> undefined behavior for the sake of "pretty syntax" (a subjective thing
> at best). Why then wouldn't you just simply write that well-defined code
> that these implementations are translating to?

It's not just syntax. If I'm not mistaken, the union-based type punning 
has advantage over memcpy - it allows the code to be constexpr.

memcpy also has potential to be a function call instead of a few 
instructions (or no instructions at all). I know many compilers are 
aware of memcpy and optimize it, but that's not something one can rely on.