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Subject: Re: [std-proposals] Allowing access to object representations
From: language.lawyer_at_[hidden]
Date: 2019-08-21 13:49:07


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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