linux-kernel - Re: [PATCH/RFC 1/2] lib: string: Remove duplicated function

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Date:	Thu, 11 Sep 2014 15:22:41 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Rasmus Villemoes <linux@...musvillemoes.dk>
Cc:	Grant Likely <grant.likely@...aro.org>,
	Andi Kleen <ak@...ux.intel.com>,
	Dan Carpenter <dan.carpenter@...cle.com>,
	"H. Peter Anvin" <hpa@...ux.intel.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH/RFC 1/2] lib: string: Remove duplicated function

On Wed, 27 Aug 2014 09:36:01 +0200 Rasmus Villemoes <linux@...musvillemoes.dk> wrote:

> lib/string.c contains two functions, strnicmp and strncasecmp, which
> do roughly the same thing, namely compare two strings
> case-insensitively up to a given bound. They have slightly different
> implementations, but the only important difference is that strncasecmp
> doesn't handle len==0 appropriately; it effectively becomes strcasecmp
> in that case. strnicmp correctly says that two strings are always
> equal in their first 0 characters.
> 
> strncasecmp is the POSIX name for this functionality. So rename the
> non-broken function to the standard name. To minimize the impact on
> the rest of the kernel (and since both are exported to modules), make
> strnicmp a wrapper for strncasecmp.

I guess it's safe to assume that nobody was depending on the
strncasecmp() bug.

The existing strnicmp() implementation is rather verbose, but I expect
that avoiding the tolower() cost where possible makes sense.

Yes, please prepare the strnicmp()->strncasecmp() patches and let's get
them merged up.  After a kernel release or two we can zap the
back-compat wrapper.


And it isn't just "out of tree modules" that we should be concerned
about - we'll commonly find that "to be in tree" code is using
interfaces which we're trying to alter or remove, so it takes a cycle
or two to get everything propagated.  Most of this code can be found in
linux-next.
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