Re: Should we use MemSet or {0} for struct initialization?

On Thu, Aug 31, 2023 at 5:34 PM Richard Guo <guofenglinux@gmail.com> wrote:
>
> While working on a bug in expandRecordVariable() I noticed that in the
> switch statement for case RTE_SUBQUERY we initialize struct ParseState
> with {0} while for case RTE_CTE we do that with MemSet.  I understand
> that there is nothing wrong with this, just cannot get away with the
> inconsistency inside the same function (sorry for the nitpicking).
>
> Do we have a preference for how to initialize structures?  From 9fd45870
> it seems that we prefer to {0}.  So here is a trivial patch doing that.
> And with a rough scan the MemSet calls in pg_stat_get_backend_subxact()
> can also be replaced with {0}, so include that in the patch too.
>
> Thanks
> Richard

If the struct has padding or aligned, {0} only guarantee the struct
members initialized to 0, while memset sets the alignment/padding
to 0 as well, but since we will not access the alignment/padding, so
they give the same effect.

I bet {0} should be faster since there is no function call, but I'm not
100% sure ;)


--
Regards
Junwang Zhao