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Wed, 24 Jul 2024 13:33:25 -0400 (EDT) X-Mailer: MessagingEngine.com Webmail Interface User-Agent: Cyrus-JMAP/3.11.0-alpha0-582-g5a02f8850-fm-20240719.002-g5a02f885 MIME-Version: 1.0 Message-Id: <24be8665-4717-4ee2-8a81-80fed5181736@app.fastmail.com> In-Reply-To: <9751d18defea406fa698630637d8e7db@AcuMS.aculab.com> References: <23bdb6fc8d884ceebeb6e8b8653b8cfe@AcuMS.aculab.com> <9751d18defea406fa698630637d8e7db@AcuMS.aculab.com> Date: Wed, 24 Jul 2024 19:32:14 +0200 From: "Arnd Bergmann" To: "David Laight" , "'linux-kernel@vger.kernel.org'" , "Linus Torvalds" Cc: "Matthew Wilcox" , "Christoph Hellwig" , "Andrew Morton" , "Andy Shevchenko" , "Dan Carpenter" , "Jason A . Donenfeld" , "'pedro.falcato@gmail.com'" , "Mateusz Guzik" , "'linux-mm@kvack.org'" Subject: Re: [PATCH 3/7] compiler.h: Add __if_constexpr(expr, if_const, if_not_const) Content-Type: text/plain X-Stat-Signature: ozowbpn7u1paquqiigo4sd6pbw4otwsh X-Rspamd-Queue-Id: 805CB1C000F X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1721842409-958142 X-HE-Meta: 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 7SGGrG2R +/+VLqxhHN9/Sv1uvL3euYVXqhIwP7wlOOHMHrlErxXk986Q0HiU1/khgfCmUFoZ8p8SMG+43rnNBS8Inu0Idy9zOqzu5ahm/SIeXitm0f054CpbteQTYGbHzxXwyTJg/cVepQ7R9+UwqnZ+ldBqFqppc4hfY2BXHRWeMzGQj/zOVBmg9D40TPbyr1tB97+6LjjVqkkJWxm+938EOCditMUgEUDIryRaRB4uedUzuilvZwKQ+A4449pDfBb+EcUfKlUH+ouNfqK7MoH1Ee2/FyxaGtA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Jul 24, 2024, at 16:29, David Laight wrote: > +#define __if_constexpr(expr, if_const, if_not_const) \ > + _Generic(0 ? ((void *)((long)(expr) * 0l)) : (char *)0, \ > + char *: (if_const), \ > + void *: (if_not_const)) > + > -#define __is_constexpr(x) \ > - (sizeof(int) == sizeof(*(8 ? ((void *)((long)(x) * 0l)) : (int *)8))) > +#define __is_constexpr(expr) __if_constexpr((expr), 1, 0) I don't immediately see anything wrong with this, but I'm still scared of any change to it, especially if this is meant to go straight into mainline. Would it be possible to do patch 4/7 without the new __if_constexpr() and instead still using __builtin_choose_expr()? Arnd