Re: [PATCH] diff: fix --color-moved-ws=allow-indentation-change

[Phillip Wood <phillip.wood@talktalk.net>]

On 04/09/2018 19:51, Phillip Wood wrote:
> Hi Stefan
> 
> On 04/09/2018 19:08, Stefan Beller wrote:
>> On Tue, Sep 4, 2018 at 6:53 AM Phillip Wood
>> <phillip.wood@talktalk.net> wrote:
>>>
>>> From: Phillip Wood <phillip.wood@dunelm.org.uk>
>>>
>>> If there is more than one potential moved block and the longest block
>>> is not the first element of the array of potential blocks then the
>>> block is cut short. With --color-moved=blocks this can leave moved
>>> lines unpainted if the shortened block does not meet the block length
>>> requirement. With --color-moved=zebra then in addition to the
>>> unpainted lines the moved color can change in the middle of a single
>>> block.
>>>
>>> Fix this by freeing the whitespace delta of the match we're discarding
>>> rather than the one we're keeping.
>>>
>>> Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
>>> ---
>>>
>>> While I was working on this I spotted a couple of other issues I don't
>>> have time to fix myself at the moment, so I thought I mention them in
>>> case someone else wants to pick them up
>>>
>>> 1) I think there is a potential memory leak at the end of
>>>     mark_color_as_moved(). If pmb_nr > 0 then the whitespace deltas
>>>     need freeing before freeing pmb itself.
>>>
>>> 2) The documentation could be improved to explain that
>>>     allow-indentation-change does not work with indentation that
>>>     contains a mix of tabs and spaces and the motivation for that
>>>     (python?) [I've got some code to add an option that supports that
>>>     which I'll post when I've written some tests after 2.19 is
>>>     released]
>>>
>>>   diff.c | 11 ++++++-----
>>>   1 file changed, 6 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/diff.c b/diff.c
>>> index 145cfbae5..4e8f725bb 100644
>>> --- a/diff.c
>>> +++ b/diff.c
>>> @@ -968,8 +968,13 @@ static void
>>> pmb_advance_or_null_multi_match(struct diff_options *o,
>>>                          /* Carry the white space delta forward */
>>>                          pmb[i]->next_line->wsd = pmb[i]->wsd;
>>>                          pmb[i] = pmb[i]->next_line;
>>> -               } else
>>> +               } else {
>>> +                       if (pmb[i]->wsd) {
>>> +                               free(pmb[i]->wsd->string);
>>> +                               FREE_AND_NULL(pmb[i]->wsd);
>>> +                       }
>>>                          pmb[i] = NULL;
>>> +               }
>>
>> I agree on this hunk, as it will fix the mem leak in the case of
>> allow-indentation-change, wondering if we need the same in
>> pmb_advance_or_null as well (and anywhere where there is a
>> 'pmb[i] = NULL' assignment outside the swapping below.).
> 
> I don't think we don't call pmb_advance_or_null() if we're using
> pmb[i]->wsd. I'm not sure if there are other sites that set 'pmb[i] =
> NULL' when pmb[i]->wsd has been allocated.

Oops there's an extra don't there. Anyway I've had a proper look through
the code and pmb_advance_or_null() is the only other place where pmb[i]
is set to NULL and that code path isn't used when pmb[i]->wsd has been
allocated. So this should be sufficient.

Best Wishes

Phillip

>>
>>
>>>          }
>>>   }
>>>
>>> @@ -990,10 +995,6 @@ static int shrink_potential_moved_blocks(struct
>>> moved_entry **pmb,
>>>
>>>                  if (lp < pmb_nr && rp > -1 && lp < rp) {
>>>                          pmb[lp] = pmb[rp];
>>> -                       if (pmb[rp]->wsd) {
>>> -                               free(pmb[rp]->wsd->string);
>>> -                               FREE_AND_NULL(pmb[rp]->wsd);
>>> -                       }
>>
>> Eh, this makes sense, though I had to think about it for a
>> while as I was confused. By the first line in the condition we
>> also keep around the ->wsd pointer as is.
> 
> Yes, it took me ages to work out that this is what was breaking the
> highlighting.
> 
> Best Wishes
> 
> Phillip
> 
>>
>> Thanks!
>> Stefan
>>