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




Hi Stefan

On 04/09/2018 19:08, Stefan Beller wrote:
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.).

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