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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-48fe537c788sm108760745e9.12.2026.05.16.01.42.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 16 May 2026 01:42:44 -0700 (PDT) Date: Sat, 16 May 2026 09:42:42 +0100 From: David Laight To: Amir Goldstein Cc: Miklos Szeredi , Christian Brauner , Jan Kara , Al Viro , Linus Torvalds , Nirmoy Das , linux-unionfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] err_ptr.h: introduce ERR_PTR_SAFE() Message-ID: <20260516094242.77d20c92@pumpkin> In-Reply-To: References: <20260514200129.94862-1-amir73il@gmail.com> <20260515193010.056ef472@pumpkin> 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=UTF-8 Content-Transfer-Encoding: quoted-printable On Fri, 15 May 2026 21:26:04 +0200 Amir Goldstein wrote: > On Fri, May 15, 2026 at 8:30=E2=80=AFPM David Laight > wrote: > > > > On Thu, 14 May 2026 22:01:29 +0200 > > Amir Goldstein wrote: > > =20 ... > > > > The object code bloat would be noticeable if this were used everywhere. > > But you could make it a bit simpler: > > if (__builtin_constant_p(__e)) > > BUILD_BUG_ON(__e && !IS_ERR_VALUE(__e)); > > else if WARN_ON(__e && !IS_ERR_VALUE(__e)) > > __e =3D -MAX_ERRNO; // Or maybe -EINVAL to stop and oth= er boundary errors > > (void *)__e; =20 >=20 > Yeh that's nicer thanks. Actually this might be better still (or just more succinct): void *__e =3D (void *)error; BUILD_BUG_ON(!statically_true(IS_ERR_OR_NULL(__e)); if (WARN_ON(!IS_ERR_OR_NULL(__e)) __e =3D (void *)-EINVAL; __e; The WARN_ON() will be optimised away (valid) constants. > > The check for constants may be fairly pointless. > > One of the static checkers may already detect the obvious fubar ERR_PTR= (EINVAL). =20 >=20 > True, but I figured it didn't add much overhead if we are placing > the runtime assertions anyway? The 'size' check in READ_ONCE() measurably slows down the kernel compilatio= n. But there are a lot of those. I think I know the main reason - the extern for the 'error message function= '. -- David >=20 > Thanks, > Amir.