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[209.85.208.169]) by smtp.gmail.com with ESMTPSA id c15sm56133ljf.1.2019.09.25.14.01.49 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 25 Sep 2019 14:01:50 -0700 (PDT) Received: by mail-lj1-f169.google.com with SMTP id e17so7143381ljf.13 for ; Wed, 25 Sep 2019 14:01:49 -0700 (PDT) X-Received: by 2002:a2e:9854:: with SMTP id e20mr218041ljj.72.1569445309746; Wed, 25 Sep 2019 14:01:49 -0700 (PDT) MIME-Version: 1.0 References: <20190925161255.1871-1-ard.biesheuvel@linaro.org> <20190925161255.1871-12-ard.biesheuvel@linaro.org> In-Reply-To: <20190925161255.1871-12-ard.biesheuvel@linaro.org> From: Linus Torvalds Date: Wed, 25 Sep 2019 14:01:33 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [RFC PATCH 11/18] int128: move __uint128_t compiler test to Kconfig To: Ard Biesheuvel Cc: Linux Crypto Mailing List , Linux ARM , Herbert Xu , David Miller , Greg KH , "Jason A . Donenfeld" , Samuel Neves , Dan Carpenter , Arnd Bergmann , Eric Biggers , Andy Lutomirski , Will Deacon , Marc Zyngier , Catalin Marinas Content-Type: text/plain; charset="UTF-8" Sender: linux-crypto-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-crypto@vger.kernel.org On Wed, Sep 25, 2019 at 9:14 AM Ard Biesheuvel wrote: > > config ARCH_SUPPORTS_INT128 > bool > + depends on !$(cc-option,-D__SIZEOF_INT128__=0) Hmm. Does this actually work? If that "depends on" now ends up being 'n', afaik the people who _enable_ it just do a select ARCH_SUPPORTS_INT128 and now you'll end up with the Kconfig erroring out with WARNING: unmet direct dependencies detected for ARCH_SUPPORTS_INT128 and then you end up with CONFIG_ARCH_SUPPORTS_INT128 anyway, instead of the behavior you _want_ to get, which is to not get that CONFIG defined at all. So I heartily agree with your intent, but I don't think that model works. I think you need to change the cases that currently do select ARCH_SUPPORTS_INT128 to instead have that cc-option test. And take all the above with a pinch of salt. Maybe what you are doing works, and I am just missing some piece of the puzzle. But I _think_ it's broken, and you didn't test with a compiler that doesn't support that thing properly. Linus