From 1f4b8568604b80f401044b8faa7a0bee567e2037 Mon Sep 17 00:00:00 2001
From: David Geier <geidav.pg@gmail.com>
Date: Sun, 18 Oct 2026 13:33:35 +0200
Subject: [PATCH v1] gen_node_support.pl skips anonymous structs/unions

---
 src/backend/nodes/gen_node_support.pl | 33 +++++++++++++++++++++++++++
 src/include/utils/rel.h               | 13 +++++++++++
 2 files changed, 46 insertions(+)

diff --git a/src/backend/nodes/gen_node_support.pl b/src/backend/nodes/gen_node_support.pl
index 0b766272018..a2d198f72b3 100644
--- a/src/backend/nodes/gen_node_support.pl
+++ b/src/backend/nodes/gen_node_support.pl
@@ -193,6 +193,9 @@ foreach my $infile (@ARGV)
 	my %my_field_types;
 	my %my_field_attrs;
 
+	# nesting depth of an anonymous union/struct; the outermost level is 1
+	my $anon_nest = 0;
+
 	# open file with name from command line, which may have a path prefix
 	open my $ifh, '<', $infile or die "could not open \"$infile\": $!";
 
@@ -229,6 +232,34 @@ foreach my $infile (@ARGV)
 		next if $line eq '';
 		next if $line =~ /^#(define|ifdef|endif)/;
 
+		# Skip anonymous union/struct blocks. These are only allowed in
+		# non-node structs, whose fields we do not process.  Anonymous unions
+		# are not supported in node structs because their copy, equal, and
+		# serialization functions cannot be generated automatically.
+		if ($in_struct)
+		{
+			if ($anon_nest > 0)
+			{
+				$anon_nest += ($line =~ tr/{//) - ($line =~ tr/}//);
+				next;
+			}
+			elsif ($anon_nest == -1)
+			{
+				die "$infile:$lineno: expected '{' after anonymous union/struct\n"
+				  unless $line =~ /^\s*\{\s*$/;
+				$anon_nest = 1;
+				next;
+			}
+			elsif ($line =~ /^\s*(?:union|struct)(?:\s*\{)?\s*$/)
+			{
+				die
+				  "$infile:$lineno: anonymous union/struct not supported in node struct \"$in_struct\"\n"
+				  if $is_node_struct;
+				$anon_nest = ($line =~ /\{/) ? 1 : -1;
+				next;
+			}
+		}
+
 		# within a struct, don't process until we have whole logical line
 		if ($in_struct && $subline > 0)
 		{
@@ -421,6 +452,7 @@ foreach my $infile (@ARGV)
 				@my_fields = ();
 				%my_field_types = ();
 				%my_field_attrs = ();
+				$anon_nest = 0;
 			}
 			# normal struct field
 			elsif ($line =~
@@ -532,6 +564,7 @@ foreach my $infile (@ARGV)
 				$in_struct = $1;
 				$in_struct_lineno = $lineno;
 				$subline = 0;
+				$anon_nest = 0;
 			}
 			# one node type typedef'ed directly from another
 			elsif ($line =~ /^typedef (\w+) (\w+);$/ and elem $1, @node_types)
diff --git a/src/include/utils/rel.h b/src/include/utils/rel.h
index 7b8c2b1e362..54d1b653133 100644
--- a/src/include/utils/rel.h
+++ b/src/include/utils/rel.h
@@ -54,6 +54,19 @@ typedef LockInfoData *LockInfo;
 
 typedef struct RelationData
 {
+	union
+	{
+		struct
+		{
+			int Foo;
+		};
+
+		struct
+		{
+			long Bar;
+		};
+	};
+
 	RelFileLocator rd_locator;	/* relation physical identifier */
 	SMgrRelation rd_smgr;		/* cached file handle, or NULL */
 	int			rd_refcnt;		/* reference count */
-- 
2.55.0