From: Alan Stern <stern@rowland.harvard.edu>
To: Horst von Brand <vonbrand@inf.utfsm.cl>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: Style question: Should one check for NULL pointers?
Date: Fri, 11 Jul 2003 17:21:33 -0400 (EDT) [thread overview]
Message-ID: <Pine.LNX.4.44L0.0307111714130.10595-100000@netrider.rowland.org> (raw)
In-Reply-To: <200307111932.h6BJWMr5004606@eeyore.valparaiso.cl>
On Fri, 11 Jul 2003, Horst von Brand wrote:
> My personal paranoia when reading code goes the other way: How can I be
> sure it won´t ever be NULL? Maybe it can't be now (and to find that out an
> hour grepping around goes by), but the very next patch introduces the
> possibility. Better have the function do an extra check, or make sure
> somehow the assumption won't _ever_ be violated. But that is a large (huge,
> even) cost, so...
Suppose something does change and your function is passed a NULL pointer
after all. What will you do about it then? Clearly this represents a
mistake on the part of the caller; are you simply going to return without
doing anything and hope that nothing else will go wrong? Or will you
return an error code and hope that a caller careless enough to pass an
invalid argument will also be careful enough to check the return code?
Quite a lot of places in the kernel do one of these (usually the first).
Neither of those options is attractive to me. I would prefer something
that leaves a clear indication that the problem exists. A logged error
message would help; a BUG_ON or segfault would be even better. This is
especially true in situations where the function in question is part of a
relatively small subsystem where you _know_ that a NULL pointer is never
valid. (It may occur, but if it does it must represent an error.)
Alan Stern
next prev parent reply other threads:[~2003-07-11 21:07 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-07-10 20:28 Style question: Should one check for NULL pointers? Alan Stern
2003-07-10 20:52 ` Eli Carter
2003-07-10 22:12 ` H. Peter Anvin
2003-07-11 2:35 ` Alan Stern
2003-07-11 14:29 ` Eli Carter
2003-07-11 15:16 ` Alan Stern
2003-07-12 18:40 ` Horst von Brand
2003-07-13 21:42 ` Alan Stern
2003-07-11 20:33 ` H. Peter Anvin
2003-07-10 22:54 ` David D. Hagood
2003-07-11 4:02 ` Hollis Blanchard
2003-07-11 4:38 ` Hua Zhong
2003-07-11 14:13 ` David D. Hagood
2003-07-11 14:52 ` Richard B. Johnson
2003-07-11 15:39 ` Alan Stern
2003-07-11 19:32 ` Horst von Brand
2003-07-11 20:36 ` H. Peter Anvin
2003-07-11 21:21 ` Alan Stern [this message]
2003-07-13 22:53 ` Ingo Oeser
[not found] <7QmZ.5RP.17@gated-at.bofh.it>
2003-07-10 21:00 ` Dennis Bliefernicht
2003-07-10 22:13 ` H. Peter Anvin
2003-07-10 22:28 ` Larry McVoy
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