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Subject: Re: [std-proposals] Allowing access to object representations
From: Krystian Stasiowski (sdkrystian_at_[hidden])
Date: 2019-08-21 13:55:42


Yes, you access the value of the object of the object, however, since its
not specified what exactly you get, it can be argued either way.
http://eel.is/c++draft/conv.lval#3.4

On Wed, Aug 21, 2019 at 2:49 PM language.lawyer--- via Std-Proposals <
std-proposals_at_[hidden]> wrote:

> On 21/08/2019 21:44, Krystian Stasiowski via Std-Proposals wrote:
> > Yes, you can. If the pointer value is unchanged, then it still points to
> the original object, and since the resulting pointer is of, say, char,
> unsigned char, or std::byte, the strict aliasing rules allow you to access
> the object.
>
> And what you will be accessing is indeed "the object", not "the first
> element" of its object representation.
>
> > On Wed, Aug 21, 2019 at 2:05 PM language.lawyer--- via Std-Proposals <
> std-proposals_at_[hidden] <mailto:std-proposals_at_[hidden]>>
> wrote:
> >
> > On 21/08/2019 11:22, sdkrystian via Std-Proposals wrote:
> > > Using reinterpret_cast, you can access the first element, but
> thats about it (pointer arithmetic is UB)
> >
> > No, u can't access "the first element".
> > reinterpret_cast won't change the pointer value, the result of
> reinterpret_cast "points to" the same object to which the argument of
> reinterpret_cast pointed to.
> > Indirection through such a pointer yields an lvalue denoting the
> object to which pointer points to and this influences lvalue-to-rvalue
> conversion applied to (or assignment through) this lvalue in a funny way.
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> >
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