From 24079682429b67a457705d6f12b13f53aaacf433 Mon Sep 17 00:00:00 2001
From: Norman Feske <norman.feske@genode-labs.com>
Date: Wed, 15 Jan 2025 16:05:52 +0100
Subject: [PATCH] sandbox: don't use Xml_node as return value

Issue #5411
---
 repos/os/src/lib/sandbox/child.h    | 24 ++++++++++++++++++++----
 repos/os/src/lib/sandbox/library.cc |  6 +++---
 2 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/repos/os/src/lib/sandbox/child.h b/repos/os/src/lib/sandbox/child.h
index 1ecf912f7a..9af64ff87b 100644
--- a/repos/os/src/lib/sandbox/child.h
+++ b/repos/os/src/lib/sandbox/child.h
@@ -50,8 +50,22 @@ class Sandbox::Child : Child_policy, Routed_service::Wakeup
 		 */
 		struct Id { unsigned value; };
 
-		struct Default_route_accessor : Interface { virtual Xml_node default_route() = 0; };
-		struct Default_caps_accessor  : Interface { virtual Cap_quota default_caps() = 0; };
+		using With_xml = Callable<void, Xml_node const &>;
+
+		struct Default_route_accessor : Interface
+		{
+			virtual void _with_default_route(With_xml::Ft const &) = 0;
+
+			void with_default_route(auto const &fn)
+			{
+				_with_default_route(With_xml::Fn { fn });
+			}
+		};
+
+		struct Default_caps_accessor : Interface
+		{
+			virtual Cap_quota default_caps() = 0;
+		};
 
 		template <typename QUOTA>
 		struct Resource_limit_accessor : Interface
@@ -140,8 +154,10 @@ class Sandbox::Child : Child_policy, Routed_service::Wakeup
 			start.with_sub_node("route",
 				[&] (Xml_node const &route) {
 					_route_model.construct(_alloc, route); },
-				[&] () {
-					_route_model.construct(_alloc, _default_route_accessor.default_route()); });
+				[&] {
+					_default_route_accessor.with_default_route([&] (Xml_node const &node) {
+						_route_model.construct(_alloc, node); });
+				});
 		}
 
 		/*
diff --git a/repos/os/src/lib/sandbox/library.cc b/repos/os/src/lib/sandbox/library.cc
index 144a9cd03b..06f863f680 100644
--- a/repos/os/src/lib/sandbox/library.cc
+++ b/repos/os/src/lib/sandbox/library.cc
@@ -189,10 +189,10 @@ struct Genode::Sandbox::Library : ::Sandbox::State_reporter::Producer,
 	/**
 	 * Default_route_accessor interface
 	 */
-	Xml_node default_route() override
+	void _with_default_route(Child::With_xml::Ft const &fn) override
 	{
-		return _default_route.constructed() ? _default_route->xml()
-		                                    : Xml_node("<empty/>");
+		if (_default_route.constructed())
+			fn(_default_route->xml());
 	}
 
 	/**