Re: Avoid memory leaks during base backups

On Thu, Oct 20, 2022 at 02:51:21PM -0400, Robert Haas wrote:
> On Thu, Oct 20, 2022 at 1:35 PM Bharath Rupireddy
> <bharath(dot)rupireddyforpostgres(at)gmail(dot)com> wrote:
>> I think elsewhere in the code we reset dangling pointers either ways -
>> before or after deleting/resetting memory context. But placing them
>> before would give us extra safety in case memory context
>> deletion/reset fails. Not sure what's the best way.
>
> I think it's OK to assume that deallocating memory will always
> succeed, so it doesn't matter whether you do it just before or just
> after that. But it's not OK to assume that *allocating* memory will
> always succeed.

AFAIK, one of the callbacks associated to a memory context could
fail, see comments before MemoryContextCallResetCallbacks() in
MemoryContextDelete(). I agree that it should not matter here, but I
think that it is better to reset the pointers before attempting the
deletion of the memory context in this case.
--
Michael