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From: David Laight <David.Laight@ACULAB.COM>
To: "'Helge Deller'" <deller@gmx.de>,
	"'Sergey Senozhatsky'" <sergey.senozhatsky.work@gmail.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>,
	"Luck, Tony" <tony.luck@intel.com>,
	"linux-ia64@vger.kernel.org" <linux-ia64@vger.kernel.org>,
	Petr Mladek <pmladek@suse.com>, Jessica Yu <jeyu@kernel.org>,
	"James E . J . Bottomley" <jejb@parisc-linux.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	"Alexei Starovoitov" <ast@kernel.org>,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	Paul Mackerras <paulus@samba.org>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH 0/5] [RFC] printk/ia64/ppc64/parisc64: let's deprecate %pF/%pf printk specifiers
Date: Wed, 20 Sep 2017 08:41:40 +0000	[thread overview]
Message-ID: <063D6719AE5E284EB5DD2968C1650D6DD007AF31@AcuExch.aculab.com> (raw)
In-Reply-To: <a7a0f1f6-781b-eba3-9b81-69b979503990@gmx.de>

From: Helge Deller
> Sent: 19 September 2017 21:08
...
> > Using 'unsigned long' for any kind of pointer is an accident
> > waiting do happen.
> > It also makes it difficult to typecheck the function calls.
> > Using 'void *' isn't any better.
> > Either a pointer to an undefined struct, or a struct containing
> > a single 'char' member, is likely to be safest.
> 
> David, you might be right in most cases, but in this case I'd prefer
> unsigned long too. I think this will create the least amount of
> typecasts here.

I've not looked at the specifics case...

Another option is using a struct with a single member and
passing it by value.
This could be used for things like user-space pointers or
even errno values.
The only problem is old ABI where even small structures are
always passed by reference.

	David

WARNING: multiple messages have this Message-ID (diff)
From: David Laight <David.Laight@ACULAB.COM>
To: 'Helge Deller' <deller@gmx.de>,
	'Sergey Senozhatsky' <sergey.senozhatsky.work@gmail.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>,
	"Luck, Tony" <tony.luck@intel.com>,
	"linux-ia64@vger.kernel.org" <linux-ia64@vger.kernel.org>,
	Petr Mladek <pmladek@suse.com>, Jessica Yu <jeyu@kernel.org>,
	"James E . J . Bottomley" <jejb@parisc-linux.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	"Alexei Starovoitov" <ast@kernel.org>,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	Paul Mackerras <paulus@samba.org>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH 0/5] [RFC] printk/ia64/ppc64/parisc64: let's deprecate %pF/%pf printk specifiers
Date: Wed, 20 Sep 2017 08:41:40 +0000	[thread overview]
Message-ID: <063D6719AE5E284EB5DD2968C1650D6DD007AF31@AcuExch.aculab.com> (raw)
In-Reply-To: <a7a0f1f6-781b-eba3-9b81-69b979503990@gmx.de>

From: Helge Deller
> Sent: 19 September 2017 21:08
...
> > Using 'unsigned long' for any kind of pointer is an accident
> > waiting do happen.
> > It also makes it difficult to typecheck the function calls.
> > Using 'void *' isn't any better.
> > Either a pointer to an undefined struct, or a struct containing
> > a single 'char' member, is likely to be safest.
>=20
> David, you might be right in most cases, but in this case I'd prefer
> unsigned long too. I think this will create the least amount of
> typecasts here.

I've not looked at the specifics case...

Another option is using a struct with a single member and
passing it by value.
This could be used for things like user-space pointers or
even errno values.
The only problem is old ABI where even small structures are
always passed by reference.

	David

  reply	other threads:[~2017-09-20  8:42 UTC|newest]

Thread overview: 47+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-09-16  3:53 [PATCH 0/5] [RFC] printk/ia64/ppc64/parisc64: let's deprecate %pF/%pf printk specifiers Sergey Senozhatsky
2017-09-16  3:53 ` Sergey Senozhatsky
2017-09-16  3:53 ` [PATCH 1/5] sections: split dereference_function_descriptor() Sergey Senozhatsky
2017-09-16  3:53   ` Sergey Senozhatsky
2017-09-16  3:53 ` [PATCH 2/5] ia64: Add .opd based function descriptor dereference Sergey Senozhatsky
2017-09-16  3:53   ` Sergey Senozhatsky
2017-09-16  3:53 ` [PATCH 3/5] powerpc64: " Sergey Senozhatsky
2017-09-16  3:53   ` Sergey Senozhatsky
2017-09-16  9:43   ` Naveen N. Rao
2017-09-16  9:55     ` Naveen N. Rao
2017-09-16 11:25     ` Sergey Senozhatsky
2017-09-16 11:25       ` Sergey Senozhatsky
2017-09-19 10:22     ` Michael Ellerman
2017-09-19 10:22       ` Michael Ellerman
2017-09-19 10:31       ` Sergey Senozhatsky
2017-09-19 10:31         ` Sergey Senozhatsky
2017-09-20  1:51         ` Michael Ellerman
2017-09-20  1:51           ` Michael Ellerman
2017-09-20  6:10           ` Sergey Senozhatsky
2017-09-20  6:10             ` Sergey Senozhatsky
2017-09-16  3:53 ` [PATCH 4/5] parisc64: " Sergey Senozhatsky
2017-09-16  3:53   ` Sergey Senozhatsky
2017-09-16  3:53 ` [PATCH 5/5] symbol lookup: use new kernel and module dereference functions Sergey Senozhatsky
2017-09-16  3:53   ` Sergey Senozhatsky
2017-09-18 17:44 ` [PATCH 0/5] [RFC] printk/ia64/ppc64/parisc64: let's deprecate %pF/%pf printk specifiers Luck, Tony
2017-09-18 17:44   ` Luck, Tony
2017-09-18 18:39   ` Helge Deller
2017-09-18 18:39     ` Helge Deller
2017-09-19  2:05     ` Sergey Senozhatsky
2017-09-19  2:05       ` Sergey Senozhatsky
2017-09-19 13:38       ` David Laight
2017-09-19 20:07         ` Helge Deller
2017-09-19 20:07           ` Helge Deller
2017-09-20  8:41           ` David Laight [this message]
2017-09-20  8:41             ` David Laight
2017-09-20 10:20             ` Helge Deller
2017-09-20 10:20               ` Helge Deller
2017-09-20 16:31               ` Sergey Senozhatsky
2017-09-20 16:31                 ` Sergey Senozhatsky
2017-09-19 14:07       ` Helge Deller
2017-09-19 14:07         ` Helge Deller
2017-09-19 20:03         ` Helge Deller
2017-09-19 20:03           ` Helge Deller
2017-09-20  0:47           ` Sergey Senozhatsky
2017-09-20  0:47             ` Sergey Senozhatsky
2017-09-19  2:08   ` Sergey Senozhatsky
2017-09-19  2:08     ` Sergey Senozhatsky

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