Re: [PATCH] db: fix unsigned char related warnings

[Christoph Hellwig <hch@lst.de>]

On Fri, Nov 03, 2023 at 01:38:13PM -0700, Darrick J. Wong wrote:
> On Fri, Nov 03, 2023 at 05:02:10PM +0100, Christoph Hellwig wrote:
> > Clean up the code in hash.c to use the normal char type for all
> > high-level code, only casting to uint8_t when calling into low-level
> > code.
> > 
> > Signed-off-by: Christoph Hellwig <hch@lst.de>
> 
> The problem is deeper than just this, but we gotta start somewhere...

Is it that much bigger?

Beѕides the usual problem of casts hiding bugs I think we are fine,
but please double check:

 - the lowlevel xfs directory entry hashing code assumes unsigned
   chars, because of that we long compiled with -funsigned-char just
   for XFS, which got obsoleted by the kernel doing it entirely
   after we've switched all the low-level code to use unsigned
   char.
 - given that traditional unix pathnames are just NULL terminate
   by arrays and the 7-bit CI code doesn't even look at the
   high bit we really don't care about signed vs unsigned except
   for the usual C pitfall when casting or shiftting

So as long as all the low-level code uses unsigned char we should
be fine.