Re: Avoid unecessary MemSet call (src/backend/utils/cache/relcache.c)

Em qui., 11 de ago. de 2022 às 07:38, Peter Eisentraut <
peter(dot)eisentraut(at)enterprisedb(dot)com> escreveu:

> On 01.08.22 19:08, Ranier Vilela wrote:
> > Like how
> >
> https://github.com/postgres/postgres/commit/9fd45870c1436b477264c0c82eb195df52bc0919
> > <
> https://github.com/postgres/postgres/commit/9fd45870c1436b477264c0c82eb195df52bc0919
> >
> > New attempt to remove more MemSet calls, that are safe.
> >
> > Attached v3 patch.
>
> Note that struct initialization does not set padding bits.

According to:
https://interrupt.memfault.com/blog/c-struct-padding-initialization

2. individually set all members to 0:

struct foo a = {
.i = 0,
.b = 0,};

Suffer from this problem.

3. use { 0 } zero-initializer, not.

So any
> struct that is used as a hash key or that goes to disk or something
> similar needs to be set with memset/MemSet instead. Various places in
> the code make explicit comments about that, which your patch deletes,
> which is a mistake. This patch needs to be adjusted carefully with this
> in mind before it can be considered.
>
I think this needs better comprovation?

regards,
Ranier Vilela