Hi Junio,
On Wed, 9 Oct 2019, Junio C Hamano wrote:
> Johannes Sixt <j6t@xxxxxxxx> writes:
>
> > We do not want to have it for *all* cases, where we return -1 - pos, but
> > only for those cases, where the result was actually encoded by
> > index_pos_to_insert_pos().
>
> Yup, I agree with you that decoder should be fed only the data
> emitted by the encoder.
>
> But shouldn't the code that yielded 'pos' that later gets decoded by
> computing "-1 -pos" without using the encoding helper be corrected
> to use the encoder instead? After all, the primary purpose of
> inventing the encoder was to catch the arith overflow, wasn't it?
That was the primary purpose of the encoder. And it is used in those
places where we want to encode _unsigned_ positions.
All of the calls to `insert_pos_to_index_pos()` that I introduced in
this here patch pass _signed_ position values, though. They cannot
overflow nor underflow because `-1 - <int>` is just the one-complement,
i.e. all bits are flipped.
Ciao,
Dscho
>
> > That excludes all cases where the argument is
> > derived from index_name_pos(), and leaves just...
> >
> >> --- a/rerere.c
> >> +++ b/rerere.c
> >> @@ -154,7 +154,7 @@ static struct rerere_dir *find_rerere_dir(const char *hex)
> >> rr_dir->status = NULL;
> >> rr_dir->status_nr = 0;
> >> rr_dir->status_alloc = 0;
> >> - pos = -1 - pos;
> >> + pos = insert_pos_to_index_pos(pos);
> >
> > ... this one...
> >
> >>
> >> /* Make sure the array is big enough ... */
> >> ALLOC_GROW(rerere_dir, rerere_dir_nr + 1, rerere_dir_alloc);
> >> diff --git a/sha1-name.c b/sha1-name.c
> >> index 49855ad24f..bee7ce39ee 100644
> >> --- a/sha1-name.c
> >> +++ b/sha1-name.c
> >> @@ -98,7 +98,7 @@ static void find_short_object_filename(struct disambiguate_state *ds)
> >> loose_objects = odb_loose_cache(odb, &ds->bin_pfx);
> >> pos = oid_array_lookup(loose_objects, &ds->bin_pfx);
> >> if (pos < 0)
> >> - pos = -1 - pos;
> >> + pos = insert_pos_to_index_pos(pos);
> >
> > ... and this one.
> >
> >> while (!ds->ambiguous && pos < loose_objects->nr) {
> >> const struct object_id *oid;
> >> oid = loose_objects->oid + pos;
> >
> > -- Hannes
>
