linux-kernel - Re: [PATCH] Fix strim() semantics for strings that have only blanks

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Message-ID: <1318581857.3362.8.camel@br98xy6r>
Date:	Fri, 14 Oct 2011 10:44:17 +0200
From:	Michael Holzheu <holzheu@...ux.vnet.ibm.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	andre.goddard@...il.com, schwidefsky@...ibm.com,
	heiko.carstens@...ibm.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Fix strim() semantics for strings that have only blanks

Hello Andrew,

On Thu, 2011-10-13 at 16:54 -0700, Andrew Morton wrote:
> On Wed, 12 Oct 2011 10:31:57 +0200
> > Also strim() explicitly does not have "__must_check", in order to use it
> > without using the return value.
> > 
> 
> This observation seems to have nothing to do with the patch?

Well, it is just a hint that it was intentionally that the return value
of strim() can be ignored and therefore I legally can use it like I do
it ;-)

> I think that strim() _should_ have __must_check annotation (which means
> that strim() simply disappears, which is good).  It is only safe to
> ignore the strim() return value if the caller knows that the string
> started with a non-space.  The number of situations where this is
> guaranteed are faily small, I suspect.

Everywhere I use that function I know that my string has only trailing
blanks (or only blanks). Therefore I think we should have a function
that just removes trailing blanks. Perhaps we should change strim() to:

void strim(char *str);

And change the three users that need the return value to use the
strstrip() instead:

grep -r " = strim(" linux-2.6
security/apparmor/lib.c:	char *name = strim(fqname);
security/apparmor/lsm.c:	args = strim(args);
security/apparmor/policy.c:	hname = strim((char *)hname);

Michael

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