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From: David Laight <David.Laight@ACULAB.COM>
To: 'Segher Boessenkool' <segher@kernel.crashing.org>, Arnd Bergmann
	<arnd@kernel.org>
CC: "linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>, "Arnd
 Bergmann" <arnd@arndb.de>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
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	<ndesaulniers@google.com>, "linux-kernel@vger.kernel.org"
	<linux-kernel@vger.kernel.org>, Nathan Chancellor <nathan@kernel.org>, "Bill
 Wendling" <morbo@google.com>, "linux-serial@vger.kernel.org"
	<linux-serial@vger.kernel.org>, Justin Stitt <justinstitt@google.com>, "Jiri
 Slaby" <jirislaby@kernel.org>
Subject: RE: [PATCH] tty: hvc-iucv: fix function pointer casts
Thread-Topic: [PATCH] tty: hvc-iucv: fix function pointer casts
Thread-Index: AQHaXrGUxAtD30hgkEO/PHRuEZrHGLEJlp9g
Date: Wed, 14 Feb 2024 09:46:33 +0000
Message-ID: <57d72e2ccc8245fe99982613a11c461c@AcuMS.aculab.com>
References: <20240213101756.461701-1-arnd@kernel.org>
 <20240213191254.GA19790@gate.crashing.org>
In-Reply-To: <20240213191254.GA19790@gate.crashing.org>
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From: Segher Boessenkool
> Sent: 13 February 2024 19:13
>=20
> On Tue, Feb 13, 2024 at 11:17:49AM +0100, Arnd Bergmann wrote:
> > clang warns about explicitly casting between incompatible function
> > pointers:
> >
> > drivers/tty/hvc/hvc_iucv.c:1100:23: error: cast from 'void (*)(const vo=
id *)' to 'void (*)(struct
> device *)' converts to incompatible function type [-Werror,-Wcast-functio=
n-type-strict]
> >  1100 |         priv->dev->release =3D (void (*)(struct device *)) kfre=
e;
> >       |                              ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>=20
> Such a cast of course is explicitly allowed by 6.3.2.3/8, only calling a
> function using a non-compatible type is UB.  This warning message is
> quite misleading.  Doubly so because of the -Werror, as always.

But it will get called using the wrong type.
And (is it) fine-ibt will reject the incorrect call.

Has clang/gcc added an attribute to 'seed' the ibt hash yet?
So that functions that are void (*)(void) can be separated?

=09David

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