C++ Logo


Advanced search

Subject: Re: reading values as bytes without memcpu, from enum unsigned char?
From: Thiago Macieira (thiago_at_[hidden])
Date: 2020-08-10 14:27:52

On Monday, 10 August 2020 12:00:10 PDT Ville Voutilainen wrote:
> > Ok, then we agree: this behaviour must not be UB. It needs to either be
> > implementation-defined or unspecified (but valid). I don't claim to know
> > the distinction between these two.
> Implementation-defined needs to be documented by the implementation,
> whereas unspecified
> does not need to be. Because it's unspecified. :P


But what guarantees does unspecified provide? Can the application rely on this
behaviour being self-consistent?

Reading from uninitialised memory produces an unspecified value and trying to
use it in a comparison or return it is UB. But simply memcpy'ing uninitialised
memory is "ok".

Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org
   Software Architect - Intel DPG Cloud Engineering

STD-DISCUSSION list run by std-discussion-owner@lists.isocpp.org

Older Archives on Google Groups