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From: Alejandro Colomar <alx+linux-hardening@kernel.org>
To: David Laight <david.laight.linux@gmail.com>
Cc: Alejandro Colomar <alx@kernel.org>,
	linux-hardening@vger.kernel.org,
	 Krzysztof Kozlowski <krzk@kernel.org>,
	"Maciej W. Rozycki" <macro@orcam.me.uk>,
	 Geert Uytterhoeven <geert@linux-m68k.org>,
	Andreas Schwab <schwab@linux-m68k.org>,
	 Andy Shevchenko <andy@kernel.org>,
	Bartosz Golaszewski <brgl@kernel.org>,
	 Daniel Scally <djrscally@gmail.com>,
	Danilo Krummrich <dakr@kernel.org>,
	 Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Hans Verkuil <hverkuil-cisco@xs4all.nl>,
	 Heikki Krogerus <heikki.krogerus@linux.intel.com>,
	Joe Perches <joe@perches.com>, Johan Hovold <johan@kernel.org>,
	 Kees Cook <kees@kernel.org>,
	Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
	 Len Brown <lenb@kernel.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	 Linus Walleij <linusw@kernel.org>,
	Namhyung Kim <namhyung@kernel.org>,
	 "Rafael J. Wysocki" <rafael@kernel.org>,
	Rob Herring <robh@kernel.org>,
	 Sakari Ailus <sakari.ailus@linux.intel.com>,
	Saravana Kannan <saravanak@kernel.org>,
	 Steven Rostedt <rostedt@goodmis.org>,
	Tom Zanussi <zanussi@kernel.org>,
	linux-acpi@vger.kernel.org,  driver-core@lists.linux.dev,
	linux-kernel@vger.kernel.org, devicetree@vger.kernel.org,
	 linux-gpio@vger.kernel.org
Subject: Re: [PATCH v3 5/5] string: Make strprefix() const-qualifier-generic
Date: Wed, 11 Nov 2026 12:28:15 +0100	[thread overview]
Message-ID: <avRQgOTnRtfec9fQ@devuan> (raw)
In-Reply-To: <20261111103438.2f822202@pumpkin>

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Hi David,

> Date: 2026-11-11 10:34:38+0000
> From: David Laight <david.laight.linux@gmail.com>
>
[...]
> > -static inline char *strprefix(const char *s, const char *prefix)
> > +#define strprefix(s, pfx)  const_cast(CQChar_of(s) *, strprefix(s, pfx))
> 
> Isn't in enough to do:
> #define strprefix(s, pfx) ((typeof(s))strprefix(s, pfx))
> 
> which correctly preserves all qualifiers.

This would return a const void* if you pass a const void*.  In general,
we shouldn't be passing a void* to a string function, but C allows this.
With CQChar_of(), you coerce a 'const void *' into a 'const char *'.

See also: <https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3998.pdf#subsection.0.7.28.5>


Cheers,
Alex

-- 
<https://www.alejandro-colomar.es>

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      reply	other threads:[~2026-11-11 11:28 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-11-10 15:33 [PATCH v3 0/5] Add strprefix() and fix a bug with it Alejandro Colomar
2026-11-10 15:33 ` [PATCH v3 1/5] string: Add strprefix(), and deprecate str_has_prefix() Alejandro Colomar
2026-11-10 15:47   ` Joe Perches
2026-11-10 16:14     ` Alejandro Colomar
2026-11-11  8:43   ` Steven Rostedt
2026-11-10 15:33 ` [PATCH v3 2/5] device property: Fix fwnode_name_eq() for empty node names Alejandro Colomar
2026-11-10 15:33 ` [PATCH v3 3/5] stddef: Add const_cast() Alejandro Colomar
2026-11-11 10:25   ` David Laight
2026-11-11 10:51     ` Alejandro Colomar
2026-11-10 15:33 ` [PATCH v3 4/5] string: Add [C]QChar_of() and QVoid_of() Alejandro Colomar
2026-11-10 15:33 ` [PATCH v3 5/5] string: Make strprefix() const-qualifier-generic Alejandro Colomar
2026-11-10 16:32   ` Joe Perches
2026-11-10 23:27     ` Alejandro Colomar
2026-11-11 10:28       ` David Laight
2026-11-11 10:59         ` Alejandro Colomar
2026-11-11 10:34   ` David Laight
2026-11-11 11:28     ` Alejandro Colomar [this message]

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