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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-483a9cbfc96sm104435485e9.15.2026.02.22.02.39.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 22 Feb 2026 02:39:10 -0800 (PST) Date: Sun, 22 Feb 2026 10:38:59 +0000 From: David Laight To: Linus Torvalds Cc: Kees Cook , linux-kernel@vger.kernel.org Subject: Re: [GIT PULL] kmalloc_obj treewide refactor for v7.0-rc1 Message-ID: <20260222103859.3b884714@pumpkin> In-Reply-To: References: <202602210108.0EABDA1CDD@keescook> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Sat, 21 Feb 2026 11:49:19 -0800 Linus Torvalds wrote: ... > IOW, how about doing something like this: > > #define pick_first(a, ...) a > #define GFP(...) pick_first(__VA_ARGS__ __VA_OPT__(,) GFP_KERNEL) > > #define kmalloc_obj(VAR_OR_TYPE, ...) \ > __alloc_objs(kmalloc, GFP(__VA_ARGS__), typeof(VAR_OR_TYPE), 1) > > and now you can just do > > a = kmalloc_obj(type); > > if you just want the default GFP_KERNEL? One problem with the above is that is you write: a = kmalloc_obj(type, GFP_KERNEL, x) then the 'x' is just silently discarded. I think you can do: #define pick_first(a, ...) a #define pick_only(a) a #define GFP(...) pick_first(__VA_OPT__(pick_only(__VA_ARGS__),) GFP_KERNEL) which generates a compile-time error if there are two (or more) arguments. It is probably wrappable as: #define default(dflt, ##__VA_ARGS__) allowing: #define GFP(...) default(GFP_KERNEL, ##__VA_ARGS__) David