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patch 8.2.2738: extending a list with itself can give wrong result

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Problem:    Extending a list with itself can give wrong result.
Solution:   Remember the item before where the insertion happens and skip to
            after the already inserted items. (closes #1112)
This commit is contained in:
Bram Moolenaar
2021-04-08 20:10:10 +02:00
parent d8db838392
commit dcae51facc
3 changed files with 24 additions and 1 deletions
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9
src/list.c
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@@ -894,6 +894,7 @@ list_extend(list_T *l1, list_T *l2, listitem_T *bef)
{
listitem_T *item;
int todo;
listitem_T *bef_prev;
// NULL list is equivalent to an empty list: nothing to do.
if (l2 == NULL || l2->lv_len == 0)
@@ -903,9 +904,15 @@ list_extend(list_T *l1, list_T *l2, listitem_T *bef)
CHECK_LIST_MATERIALIZE(l1);
CHECK_LIST_MATERIALIZE(l2);
// When exending a list with itself, at some point we run into the item
// that was before "bef" and need to skip over the already inserted items
// to "bef".
bef_prev = bef == NULL ? NULL : bef->li_prev;
// We also quit the loop when we have inserted the original item count of
// the list, avoid a hang when we extend a list with itself.
for (item = l2->lv_first; item != NULL && --todo >= 0; item = item->li_next)
for (item = l2->lv_first; item != NULL && --todo >= 0;
item = item == bef_prev ? bef : item->li_next)
if (list_insert_tv(l1, &item->li_tv, bef) == FAIL)
return FAIL;
return OK;