getting the on-disk case for a path

[Glenn Strauss]

On Thu, Aug 07, 2025 at 05:31:11PM -0700, Jeremy Drake via Cygwin wrote:
> On a case-insensitive but case-preserving filesystem, is there a Cygwin
> API to get the on-disk case for a given path?  It seems like `realpath`
> ought to do it but running
> $ touch case-test
> $ realpath CASE-TEST
> returns CASE-TEST.  Regardless, canonicalize_file_name or realpath may not
> be what I want because it would dereference symlinks.
> 
> Background: I'm trying to debug some test failures in Clang, due to a
> warning that's supposed to be issued when you #include "foo.h" but the
> file on disk that it opened is "Foo.h".

Not directly answering your initial question, but I have found the -H
compiler flag useful for troubleshooting from where files are included:
If you change the compiler command line from gcc/clang "... -o foo.o"
to "-H", then the compiler outputs a list of header files paths as they
are included by the preprocessor.

Cheers, Glenn