Re: BUG #17858: ExecEvalArrayExpr() leaves uninitialised memory for multidim array with nulls

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От	Alexander Lakhin
Тема	Re: BUG #17858: ExecEvalArrayExpr() leaves uninitialised memory for multidim array with nulls
Дата	21 марта 2023 г. 13:00:00
Msg-id	4240d86f-7e9f-388b-fd96-f8944860c0f5@gmail.com обсуждение
Ответ на	Re: BUG #17858: ExecEvalArrayExpr() leaves uninitialised memory for multidim array with nulls (Richard Guo <guofenglinux@gmail.com>)
Ответы	Re: BUG #17858: ExecEvalArrayExpr() leaves uninitialised memory for multidim array with nulls
Список	pgsql-bugs

Дерево обсуждения

Hi Richard,
21.03.2023 14:52, Richard Guo wrote:

Nice catch. This can also be seen on master.

I searched the codes a little bit and found that in array_set_slice()
and array_set_element() the 'newarray' is allocated with palloc0 and
then the nulls bitmap is zeroed with

MemSet(nullbitmap, 0, (nitems + 7) / 8);

if havenulls is true. I wonder if we can do the same here.

I'm afraid that zeroing only bytes behind nitems bits is not enough, as outDatum() doesn't bother to calculate the exact size of nulls bitmap, it just outputs all bytes of a datum (40 bytes in that case):
   length = datumGetSize(value, typbyval, typlen);
...
            for (i = 0; i < length; i++)
               appendStringInfo(str, "%d ", (int) (s[i]));

Best regards,
Alexander

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Re: BUG #17858: ExecEvalArrayExpr() leaves uninitialised memory for multidim array with nulls