Re: [PATCH v3 3/3] core: convert build-time USE_NSEC into runtime core.useNanosec

> On Wed, Aug 19, 2026 at 4:24 AM Patrick Steinhardt <ps@pks.im> wrote:
> > On Tue, Aug 18, 2026 at 10:59:47AM -0400, D. Ben Knoble wrote:
> > > diff --git a/read-cache.c b/read-cache.c
> > > index 6c449f393d..31888f77ee 100644
> > > --- a/read-cache.c
> > > +++ b/read-cache.c
> > > @@ -353,12 +353,18 @@ static int ce_match_stat_basic(const struct cache_entry *ce, struct stat *st)
> > >  static int is_racy_stat(const struct index_state *istate,
> > >                       const struct stat_data *sd)
> > >  {
> > > +#ifndef NO_NSEC
> > > +     int use_nsec = repo_config_values(istate->repo)->use_nanosec;
> > > +#endif
> > > +
> > >       return (istate->timestamp.sec &&
> > > -#ifdef USE_NSEC
> > > -              /* nanosecond timestamped files can also be racy! */
> > > -             (istate->timestamp.sec < sd->sd_mtime.sec ||
> > > -              (istate->timestamp.sec == sd->sd_mtime.sec &&
> > > -               istate->timestamp.nsec <= sd->sd_mtime.nsec))
> > > +#ifndef NO_NSEC
> > > +             /* nanosecond timestamped files can also be racy! */
> > > +             use_nsec
> > > +             ? (istate->timestamp.sec < sd->sd_mtime.sec ||
> > > +                (istate->timestamp.sec == sd->sd_mtime.sec &&
> > > +                 istate->timestamp.nsec <= sd->sd_mtime.nsec))
> > > +             : istate->timestamp.sec <= sd->sd_mtime.sec
> > >  #else
> > >               istate->timestamp.sec <= sd->sd_mtime.sec
> > >  #endif
> >
> > I think this would be a bit more readable if we had a single NO_NSEC
> > block.
> 
> I'm not sure what "single block" means here, but I think the plan (see
> reply to Junio) is to make this more readable by not needing
> pre-processor directives at all.

> > There's one more site in "builtin/update-index.c" where we mention
> > USE_NSEC that wasn't updated as part of this patch.
> 
> Oh, did I miss one? The only spot I saw in builtin/update-index.c that
> mentions USE_NSEC is a comment that I'm sure patch 3 updated. Maybe
> you were thinking of that, or maybe you know of something I left out?
> (That is, locally on this branch, "git grep USE_NSEC" returns one hit
> in Documentation/RelNotes/2.5.0.adoc.)