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

["Darrick J. Wong" <djwong@kernel.org>]

On Mon, Nov 06, 2023 at 07:59:39AM +0100, Christoph Hellwig wrote:
> 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.

I'll go take a look, though that might take a day or two.

--D