Re: [PATCH 1/5] grep: stop modifying buffer in strip_timestamp

From: Jeff King <peff@peff.net>
Date: Sep 21, 2021, 05:43 UTC
Message-ID: <YUlw6V7AL8l6mbSh@coredump.intra.peff.net>
In-Reply-To: <CAPig+cQnC1LLPtuC0qVX7EQ_ki4pev6scRox3utA45XeLHfGig@mail.gmail.com>

On Tue, Sep 21, 2021 at 01:24:41AM -0400, Eric Sunshine wrote:

Show 17 quoted lines

> On Tue, Sep 21, 2021 at 1:18 AM Carlo Arenas <carenas@gmail.com> wrote:
> > On Mon, Sep 20, 2021 at 9:09 PM Jeff King <peff@peff.net> wrote:
> > > @@ -971,7 +966,7 @@ static int match_one_pattern(struct grep_pat *p, char *bol, char *eol,
> > >                 switch (p->field) {
> > >                 case GREP_HEADER_AUTHOR:
> > >                 case GREP_HEADER_COMMITTER:
> > > -                       saved_ch = strip_timestamp(bol, &eol);
> > > +                       strip_timestamp(bol, &eol);
> >
> > Why not something like (plus added error handling, even if it seems
> > the original didn't have them)?
> >
> >   eol = strrchr(bol, '>');
> 
> strrchr() would search backward from the NUL, not from `eol`, thus
> would not be a faithful conversion (and might not be safe, though I
> didn't dig through all the callers).

Right. The point is that we should be respecting "eol" here in the first place. Plus the final result is the character _after_ the '>'. Plus when it returns NULL, you'd want to leave "eol" untouched (stripping nothing).

So yeah, I'm sure it could be rewritten around memrchr() or something, but I doubt it would be much shorter, and the chance of introducing an off-by-one seems non-trivial. :)

-Peff