locale-aware string comparisons

Given (just) the data in 10646, Unicode and cldr, are there any locales
where a case-insensitive match should be different than a case-preserving
match of the results of lower-casing the two strings?

Ie, in terms of locale-aware versions of the typical libc functions,
should strcasecmp(s1,s2) ever generate different results than
strcmp(tolower(s1),tolower(s2)) or strcmp(toupper(s1),toupper(s2))?
(By mentioning strcmp() et al, I do not exclude mb or w versions of
those functions.)

And to be clear, the questions isn't about any specific, existing
implementation but only about what the 10646, unicode and cldr suite
of standards have to say on the matter.

Thanks,

-JimC

-- 
James Cloos <cloos_at_jhcloos.com>         OpenPGP: 1024D/ED7DAEA6