| From: | Oleksandr Shulgin <oleksandr(dot)shulgin(at)zalando(dot)de> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | jesper(dot)pedersen(at)redhat(dot)com, David Rowley <david(dot)rowley(at)2ndquadrant(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, Robert Haas <robertmhaas(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: POC: converting Lists into arrays |
| Date: | 2019-07-02 07:35:18 |
| Message-ID: | CACACo5QTvn7JbtJUBXtfb-p3jA6c0pJUk_-4BOHFqokok6m3Rg@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Tue, Jul 2, 2019 at 1:27 AM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> So I think this is a win, and attached is v7.
>
Not related to the diff v6..v7, but shouldn't we throw additionally a
memset() with '\0' before calling pfree():
+ ListCell *newelements;
+
+ newelements = (ListCell *)
+ MemoryContextAlloc(GetMemoryChunkContext(list),
+ new_max_len * sizeof(ListCell));
+ memcpy(newelements, list->elements,
+ list->length * sizeof(ListCell));
+ pfree(list->elements);
+ list->elements = newelements;
Or is this somehow ensured by debug pfree() implementation or does it work
differently together with Valgrind?
Otherwise it seems that the calling code can still be hanging onto a list
element from a freed chunk and (rather) happily accessing it, as opposed to
almost ensured crash if that is zeroed before returning from enlarge_list().
Cheers,
--
Alex
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