patchdiff: fix --color-moved-ws=allow-indentation-change

>
> 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;
> +               }

>         }
>  }
>
> @@ -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);
> -                       }

> 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.).

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

> 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
>>

>>  [...] So this should be sufficient.
>
> Yup.
> Thanks for keeping track of this patch, as I lost track of it.
>
> thanks,
> Stefan

>
> Stefan Beller <sbeller@google.com> writes:
>
> >>  [...] So this should be sufficient.
> >
> > Yup.
> > Thanks for keeping track of this patch, as I lost track of it.
> >
> > thanks,
> > Stefan
>
> So does the above exchange mean that
> <20180904135258.31300-1-phillip.wood@talktalk.net> is ready to go
> with your Acked-by?

> On Tue, Sep 11, 2018 at 11:16 AM Junio C Hamano <gitster@pobox.com> wrote:
>>
>> Stefan Beller <sbeller@google.com> writes:
>>
>> >>  [...] So this should be sufficient.
>> >
>> > Yup.
>> > Thanks for keeping track of this patch, as I lost track of it.
>> >
>> > thanks,
>> > Stefan
>>
>> So does the above exchange mean that
>> <20180904135258.31300-1-phillip.wood@talktalk.net> is ready to go
>> with your Acked-by?
>
> Acked-by: Stefan Beller <sbeller@google.com