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

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

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.

> 
> 
>>          }
>>   }
>>
>> @@ -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
>