Re: per backend WAL statistics

Hi,

On Tue, Mar 11, 2025 at 11:14:24PM -0400, Tom Lane wrote:
> Michael Paquier <michael(at)paquier(dot)xyz> writes:
> > And I guess that we're OK here, so applied. That should be the last
> > one.
>
> Quite a few buildfarm members are not happy about the initialization
> that 9a8dd2c5a added to PendingBackendStats. For instance [1]:
>
> gcc -std=gnu99 -Wall -Wmissing-prototypes -Wpointer-arith -Wdeclaration-after-statement -Werror=vla -Wendif-labels -Wmissing-format-attribute -Wformat-security -fno-strict-aliasing -fwrapv -fexcess-precision=standard -g -O2 -I. -I. -I../../../../src/include -D_GNU_SOURCE -I/usr/include/libxml2 -c -o pgstat_backend.o pgstat_backend.c
> pgstat_backend.c:39:1: warning: missing braces around initializer [-Wmissing-braces]
> static PgStat_BackendPending PendingBackendStats = {0};
> ^
> pgstat_backend.c:39:1: warning: (near initialization for \342\200\230PendingBackendStats.pending_io\342\200\231) [-Wmissing-braces]
>
> I guess that more than one level of braces is needed for this to
> be fully correct?

Thanks for the report! I think that it's better to remove the PendingBackendStats
initializer (instead of adding extra braces). The reason is that I'm concerned
about padding bytes (that could be added to the struct in the future) not being
zeroed (see [1]).

Done that way in the attached.

[1]: https://www.postgresql.org/message-id/Z8/W73%2BHVo%2B/pKHZ%40ip-10-97-1-34.eu-west-3.compute.internal

Regards,

--
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com