Re: [PATCH 00/22] treewide: Replace strnicmp with strncasecmp

[Rasmus Villemoes <linux@rasmusvillemoes.dk>]

On Tue, Sep 16 2014, Theodore Ts'o <tytso@mit.edu> wrote:

> On Tue, Sep 16, 2014 at 10:51:14PM +0200, Rasmus Villemoes wrote:
>> The kernel used to contain two functions for length-delimited,
>> case-insensitive string comparison, strnicmp with correct semantics
>> and a slightly buggy strncasecmp. The latter is the POSIX name, so
>> strnicmp was renamed to strncasecmp, and strnicmp made into a wrapper
>> for the new strncasecmp to avoid breaking existing users.
>
> For the sake of those people who need to review the patches, can you
> say a bit more about the difference in semantics between strnicmp and
> strncasecmp, and why it's safe to do a global search and replace
> without worrying about the semantic differences?
>

The new strncasecmp is exactly the old strnicmp, making
s/strnicmp/strncasecmp/g a semantic noop. But of course it needs to be
applied after the renaming. Andrew said he'd take these follow-up
patches and make sure they're applied in proper order. Even without the
follow-up patches, strnicmp users shouldn't be affected except for a
very small extra indirection overhead.

The two functions behaved identically whenever the length argument was
non-zero. For len==0, the old strncasecmp however effectively became
strcasecmp.

http://thread.gmane.org/gmane.linux.kernel/1775150/focus=1775152

Thanks,
Rasmus