https://bugs.winehq.org/show_bug.cgi?id=45322
--- Comment #10 from Henri Verbeet hverbeet@gmail.com --- (In reply to Jactry Zeng from comment #9)
Attachment is a testcase for describing it, you can compile it with `gcc test_strncasecmp.c -o test_strncasecmp -Wall`. On my Debian with 2.28-8 it return -32 for the first comparing. And on macOS it returned 0, since macOS was using a different C library implementation.
I only have limited experience with Turkish orthography, but my understanding is that the correct capitalisation of 'i' would be 'İ', while 'I' would be the capitalisation of 'ı'.
Based on that, the glibc result is what I would expect, and the macOS result isn't.