Srinath Reddy Sadipiralla <[email protected]> wrote:

> Hi Tom,
> 
> On Tue, Apr 7, 2026 at 10:14 AM Tom Lane <[email protected]> wrote:
> 
>  Maybe you saw this already, but BF member skink is failing on
>  src/test/modules/injection_points/specs/repack.spec:
> 
>  
> https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=skink&dt=2026-04-06%2022%3A50%3A41
> 
> i looked into this , it seems like valgrind catches the uninitialised padding 
> bytes, which
> repack worker is writing using BufFileWrite, it seems this fix solved the 
> problem.
> 
> diff --git a/src/backend/utils/time/snapmgr.c 
> b/src/backend/utils/time/snapmgr.c
> index 2e6197f5f35..f5682b87626 100644
> --- a/src/backend/utils/time/snapmgr.c
> +++ b/src/backend/utils/time/snapmgr.c
> @@ -1739,6 +1739,8 @@ SerializeSnapshot(Snapshot snapshot, char 
> *start_address)
>  
>   Assert(snapshot->subxcnt >= 0);
>  
> + MemSet(&serialized_snapshot, 0, sizeof(SerializedSnapshotData));
> +
>   /* Copy all required fields */
>   serialized_snapshot.xmin = snapshot->xmin;
>   serialized_snapshot.xmax = snapshot->xmax;
> 
> thoughts?

Could you reproduce the failure in your environment?

I haven't thought of this explanation because BufFileWrite() only copies the
data to a buffer in the BufFile structure and BufFileDumpBuffer() writes the
buffer. Maybe valgrind is able to track the copying?

-- 
Antonin Houska
Web: https://www.cybertec-postgresql.com


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