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




On Tue, Sep 4, 2018 at 6:53 AM Phillip Wood <phillip.wood@xxxxxxxxxxxx> wrote:
>
> From: Phillip Wood <phillip.wood@xxxxxxxxxxxxx>
>
> 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@xxxxxxxxxxxxx>
> ---
>
> 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.

Thanks!
Stefan