linux-kernel - Re: [BUG] [5.15] Compilation error in arch/x86/kvm/mmu/spte.h with clang-14

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Date:   Fri, 15 Oct 2021 11:17:22 +0200
From:   Christophe de Dinechin <cdupontd@...hat.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Nick Desaulniers <ndesaulniers@...gle.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Jim Mattson <jmattson@...gle.com>, torvic9@...lbox.org,
        "vkuznets@...hat.com" <vkuznets@...hat.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "bp@...en8.de" <bp@...en8.de>
Subject: Re: [BUG] [5.15] Compilation error in arch/x86/kvm/mmu/spte.h with
 clang-14



> On 14 Oct 2021, at 22:50, Paolo Bonzini <pbonzini@...hat.com> wrote:
> 
> On 14/10/21 21:06, Nick Desaulniers wrote:
>>> If we want to fix this, my vote is for casting to an int and updating the comment
>> At the least, I think bitwise operations should only be performed on
>> unsigned types.
> 
> This is not a bitwise operation, it's a non-short-circuiting boolean operation.  I'll apply Jim's suggestion.

What about making it an inline function, which would require evaluation of arguments:

	static __always_inline bool BITWISE_BOOLEAN_OR(bool a, bool b)
	{
	    return a || b; // Safe here, because arguments have been evaluated
	}

Suggesting that because I'm always nervous about casts in macros hiding something that the type  system would otherwise catch.


Christophe
> 
> Paolo
>