From a60e3cb4911911fff968eadb4e0f318c2edd1dbb Mon Sep 17 00:00:00 2001
From: Heikki Linnakangas <heikki.linnakangas@iki.fi>
Date: Thu, 12 Mar 2026 14:40:25 +0200
Subject: [PATCH 3/4] XXX: a few more places that maybe need clearing?

I spotted these by doing 'pahole bin/postgres', and searching for
"xl_*" structs that have padding in them. Then I searched where
they're initialized.
---
 src/backend/access/hash/hashinsert.c      | 2 ++
 src/backend/access/heap/heapam.c          | 6 ++++++
 src/backend/access/heap/rewriteheap.c     | 2 ++
 src/backend/access/transam/twophase.c     | 2 ++
 src/backend/commands/tablecmds.c          | 2 ++
 src/backend/replication/logical/message.c | 2 ++
 6 files changed, 16 insertions(+)

diff --git a/src/backend/access/hash/hashinsert.c b/src/backend/access/hash/hashinsert.c
index 0cefbacc96e..45e613ceddb 100644
--- a/src/backend/access/hash/hashinsert.c
+++ b/src/backend/access/hash/hashinsert.c
@@ -426,6 +426,8 @@ _hash_vacuum_one_page(Relation rel, Relation hrel, Buffer metabuf, Buffer buf)
 			xl_hash_vacuum_one_page xlrec;
 			XLogRecPtr	recptr;
 
+			/* XXX: clear padding? */
+
 			xlrec.isCatalogRel = RelationIsAccessibleInLogicalDecoding(hrel);
 			xlrec.snapshotConflictHorizon = snapshotConflictHorizon;
 			xlrec.ntuples = ndeletable;
diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index b11dba81aef..54943be6126 100644
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -2616,6 +2616,12 @@ heap_multi_insert(Relation relation, TupleTableSlot **slots, int ntuples,
 			xlrec = (xl_heap_multi_insert *) scratchptr;
 			scratchptr += SizeOfHeapMultiInsert;
 
+			/*
+			 * XXX: need to clear padding in xl_heap_multi_insert? The scratch
+			 * area was zeroed at the top of the function, but we're reusing
+			 * it for multiple records.
+			 */
+
 			/*
 			 * Allocate offsets array. Unless we're reinitializing the page,
 			 * in that case the tuples are stored in order starting at
diff --git a/src/backend/access/heap/rewriteheap.c b/src/backend/access/heap/rewriteheap.c
index 6b19ac3030d..b6d784572ec 100644
--- a/src/backend/access/heap/rewriteheap.c
+++ b/src/backend/access/heap/rewriteheap.c
@@ -842,6 +842,8 @@ logical_heap_rewrite_flush_mappings(RewriteState state)
 		else
 			dboid = MyDatabaseId;
 
+		/* XXX: clear padding? */
+
 		xlrec.num_mappings = num_mappings;
 		xlrec.mapped_rel = RelationGetRelid(state->rs_old_rel);
 		xlrec.mapped_xid = src->xid;
diff --git a/src/backend/access/transam/twophase.c b/src/backend/access/transam/twophase.c
index 55b9f38927d..c22ab93965e 100644
--- a/src/backend/access/transam/twophase.c
+++ b/src/backend/access/transam/twophase.c
@@ -1076,6 +1076,8 @@ StartPrepare(GlobalTransaction gxact)
 
 	records.total_len = 0;
 
+	/* XXX: Clear padding? */
+
 	/* Create header */
 	hdr.magic = TWOPHASE_MAGIC;
 	hdr.total_len = 0;			/* EndPrepare will fill this in */
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index a7c32679b22..1bf59f77ae1 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -2325,6 +2325,8 @@ ExecuteTruncateGuts(List *explicit_rels,
 		foreach(cell, relids_logged)
 			logrelids[i++] = lfirst_oid(cell);
 
+		/* XXX: clear padding? */
+
 		xlrec.dbId = MyDatabaseId;
 		xlrec.nrelids = list_length(relids_logged);
 		xlrec.flags = 0;
diff --git a/src/backend/replication/logical/message.c b/src/backend/replication/logical/message.c
index 06825d66e7f..40d032a4ffc 100644
--- a/src/backend/replication/logical/message.c
+++ b/src/backend/replication/logical/message.c
@@ -55,6 +55,8 @@ LogLogicalMessage(const char *prefix, const char *message, size_t size,
 		GetCurrentTransactionId();
 	}
 
+	/* XXX: clear padding? */
+
 	xlrec.dbId = MyDatabaseId;
 	xlrec.transactional = transactional;
 	/* trailing zero is critical; see logicalmsg_desc */
-- 
2.47.3