linux-kernel - RE: [PATCH v2] x86/fpu: use _Alignof to avoid UB in TYPE

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Message-Id: <20220927170702.209578-1-me@inclyc.cn>
Date:   Wed, 28 Sep 2022 01:07:02 +0800
From:   YingChi Long <me@...lyc.cn>
To:     me@...lyc.cn
Cc:     bp@...en8.de, chang.seok.bae@...el.com,
        dave.hansen@...ux.intel.com, david.laight@...lab.com,
        hpa@...or.com, linux-kernel@...r.kernel.org, mingo@...hat.com,
        ndesaulniers@...gle.com, pbonzini@...hat.com, tglx@...utronix.de,
        x86@...nel.org
Subject: RE: [PATCH v2] x86/fpu: use _Alignof to avoid UB in TYPE_ALIGN

In LLVM Phab we have discussed difference between using offsetof and _Alignof.

> Technically there's no requirement that they return the same value (the
> structure could insert arbitrary padding, including no padding), so it's
> theoretically possible they return different values. But I can't think of a
> situation in which you'd get a different answer from `TYPE_ALIGN` as you
> would get from `_Alignof`.

Link: https://reviews.llvm.org/D133574#3815253