diff --git a/src/buddies/src/bd/strmxor.cc b/src/buddies/src/bd/strmxor.cc
index 1e5cf7722..6bed6fa16 100644
--- a/src/buddies/src/bd/strmxor.cc
+++ b/src/buddies/src/bd/strmxor.cc
@@ -707,7 +707,6 @@ bool run_deep_xor (const XORData &xor_data)
 {
   db::DeepShapeStore dss;
   dss.set_threads (xor_data.threads);
-  dss.set_keep_layouts (true);  //  avoids excessive cell mapping
 
   double dbu = std::min (xor_data.layout_a->dbu (), xor_data.layout_b->dbu ());
 
diff --git a/src/db/db/dbDeepShapeStore.cc b/src/db/db/dbDeepShapeStore.cc
index ddda1ee2c..c22f1ba70 100644
--- a/src/db/db/dbDeepShapeStore.cc
+++ b/src/db/db/dbDeepShapeStore.cc
@@ -426,13 +426,13 @@ static unsigned int init_layer (db::Layout &layout, const db::RecursiveShapeIter
 }
 
 DeepShapeStore::DeepShapeStore ()
-  : m_keep_layouts (false)
+  : m_keep_layouts (true)
 {
   ++s_instance_count;
 }
 
 DeepShapeStore::DeepShapeStore (const std::string &topcell_name, double dbu)
-  : m_keep_layouts (false)
+  : m_keep_layouts (true)
 {
   ++s_instance_count;
 
diff --git a/src/db/db/gsiDeclDbTilingProcessor.cc b/src/db/db/gsiDeclDbTilingProcessor.cc
index 39b17def5..e3a3e26db 100644
--- a/src/db/db/gsiDeclDbTilingProcessor.cc
+++ b/src/db/db/gsiDeclDbTilingProcessor.cc
@@ -417,6 +417,9 @@ Class<db::TilingProcessor> decl_TilingProcessor ("db", "TilingProcessor",
     "Regions don't always come with a database unit, hence a database unit should be specified with the \\dbu= method unless "
     "a layout object is specified as input too.\n"
     "\n"
+    "Caution: the Region object must stay valid during the lifetime of the tiling processor. Take care to store it in "
+    "a variable to prevent early destruction of the Region object. Not doing so may crash the application.\n"
+    "\n"
     "The name specifies the variable under which the input can be used in the scripts."
   ) + 
   method_ext ("input", &tp_input9, gsi::arg ("name"), gsi::arg ("region"), gsi::arg ("trans"),
@@ -425,6 +428,9 @@ Class<db::TilingProcessor> decl_TilingProcessor ("db", "TilingProcessor",
     "Regions don't always come with a database unit, hence a database unit should be specified with the \\dbu= method unless "
     "a layout object is specified as input too.\n"
     "\n"
+    "Caution: the Region object must stay valid during the lifetime of the tiling processor. Take care to store it in "
+    "a variable to prevent early destruction of the Region object. Not doing so may crash the application.\n"
+    "\n"
     "The name specifies the variable under which the input can be used in the scripts."
     "\n"
     "This variant allows one to specify an additional transformation too. It has been introduced in version 0.23.2.\n"
@@ -435,6 +441,9 @@ Class<db::TilingProcessor> decl_TilingProcessor ("db", "TilingProcessor",
     "Edge collections don't always come with a database unit, hence a database unit should be specified with the \\dbu= method unless "
     "a layout object is specified as input too.\n"
     "\n"
+    "Caution: the Edges object must stay valid during the lifetime of the tiling processor. Take care to store it in "
+    "a variable to prevent early destruction of the Edges object. Not doing so may crash the application.\n"
+    "\n"
     "The name specifies the variable under which the input can be used in the scripts."
   ) + 
   method_ext ("input", &tp_input11, gsi::arg ("name"), gsi::arg ("edges"), gsi::arg ("trans"),
@@ -443,6 +452,9 @@ Class<db::TilingProcessor> decl_TilingProcessor ("db", "TilingProcessor",
     "Edge collections don't always come with a database unit, hence a database unit should be specified with the \\dbu= method unless "
     "a layout object is specified as input too.\n"
     "\n"
+    "Caution: the Edges object must stay valid during the lifetime of the tiling processor. Take care to store it in "
+    "a variable to prevent early destruction of the Edges object. Not doing so may crash the application.\n"
+    "\n"
     "The name specifies the variable under which the input can be used in the scripts."
     "\n"
     "This variant allows one to specify an additional transformation too. It has been introduced in version 0.23.2.\n"
@@ -454,6 +466,9 @@ Class<db::TilingProcessor> decl_TilingProcessor ("db", "TilingProcessor",
     "Edge pair collections don't always come with a database unit, hence a database unit should be specified with the \\dbu= method unless "
     "a layout object is specified as input too.\n"
     "\n"
+    "Caution: the EdgePairs object must stay valid during the lifetime of the tiling processor. Take care to store it in "
+    "a variable to prevent early destruction of the EdgePairs object. Not doing so may crash the application.\n"
+    "\n"
     "The name specifies the variable under which the input can be used in the scripts."
     "\n"
     "This variant has been introduced in version 0.27.\n"
@@ -464,6 +479,9 @@ Class<db::TilingProcessor> decl_TilingProcessor ("db", "TilingProcessor",
     "Edge pair collections don't always come with a database unit, hence a database unit should be specified with the \\dbu= method unless "
     "a layout object is specified as input too.\n"
     "\n"
+    "Caution: the EdgePairs object must stay valid during the lifetime of the tiling processor. Take care to store it in "
+    "a variable to prevent early destruction of the EdgePairs object. Not doing so may crash the application.\n"
+    "\n"
     "The name specifies the variable under which the input can be used in the scripts."
     "\n"
     "This variant has been introduced in version 0.27.\n"
@@ -474,6 +492,9 @@ Class<db::TilingProcessor> decl_TilingProcessor ("db", "TilingProcessor",
     "Text collections don't always come with a database unit, hence a database unit should be specified with the \\dbu= method unless "
     "a layout object is specified as input too.\n"
     "\n"
+    "Caution: the Texts object must stay valid during the lifetime of the tiling processor. Take care to store it in "
+    "a variable to prevent early destruction of the Texts object. Not doing so may crash the application.\n"
+    "\n"
     "The name specifies the variable under which the input can be used in the scripts."
     "\n"
     "This variant has been introduced in version 0.27.\n"
@@ -484,6 +505,9 @@ Class<db::TilingProcessor> decl_TilingProcessor ("db", "TilingProcessor",
     "Text collections don't always come with a database unit, hence a database unit should be specified with the \\dbu= method unless "
     "a layout object is specified as input too.\n"
     "\n"
+    "Caution: the Texts object must stay valid during the lifetime of the tiling processor. Take care to store it in "
+    "a variable to prevent early destruction of the Texts object. Not doing so may crash the application.\n"
+    "\n"
     "The name specifies the variable under which the input can be used in the scripts."
     "\n"
     "This variant has been introduced in version 0.27.\n"
diff --git a/src/db/unit_tests/dbDeepShapeStoreTests.cc b/src/db/unit_tests/dbDeepShapeStoreTests.cc
index c629f2c6b..223ca3ac1 100644
--- a/src/db/unit_tests/dbDeepShapeStoreTests.cc
+++ b/src/db/unit_tests/dbDeepShapeStoreTests.cc
@@ -73,6 +73,7 @@ static size_t shapes_in_top (const db::Layout &layout, unsigned int layer)
 TEST(2_RefCounting)
 {
   db::DeepShapeStore store;
+  store.set_keep_layouts (false);
   db::Layout layout;
 
   unsigned int l1 = layout.insert_layer ();
diff --git a/src/drc/drc/built-in-macros/_drc_complex_ops.rb b/src/drc/drc/built-in-macros/_drc_complex_ops.rb
index e83f71d60..5014cf5ef 100644
--- a/src/drc/drc/built-in-macros/_drc_complex_ops.rb
+++ b/src/drc/drc/built-in-macros/_drc_complex_ops.rb
@@ -232,15 +232,15 @@ class DRCOpNode
   attr_accessor :description
   attr_accessor :engine
   
-  def initialize(engine, node = nil)
-    @node = node
+  def initialize(engine, &factory)
+    @factory = factory
     self.engine = engine
     self.description = "Basic"
   end
   
   def create_node(cache)
     n = cache[self.object_id]
-    if !n
+    if !n || n.destroyed?
       n = self.do_create_node(cache)
       cache[self.object_id] = n
     end
@@ -248,7 +248,7 @@ class DRCOpNode
   end
   
   def do_create_node(cache)
-    @node
+    @factory.call
   end
   
   def dump(indent)
@@ -362,8 +362,8 @@ CODE
         return self.inverted
       else
         # TODO: what if the expression isn't region?
-        empty = RBA::CompoundRegionOperationNode::new_empty(RBA::CompoundRegionOperationNode::ResultType::Region)
-        DRCOpNodeCase::new(@engine, [ self, DRCOpNode::new(@engine, empty), @engine.primary ])
+        empty = DRCOpNode::new(@engine) { RBA::CompoundRegionOperationNode::new_empty(RBA::CompoundRegionOperationNode::ResultType::Region) }
+        DRCOpNodeCase::new(@engine, [ self, empty, @engine.primary ])
       end
     end
   end
diff --git a/src/drc/drc/built-in-macros/_drc_cop_integration.rb b/src/drc/drc/built-in-macros/_drc_cop_integration.rb
index e299350f7..2f47e052f 100644
--- a/src/drc/drc/built-in-macros/_drc_cop_integration.rb
+++ b/src/drc/drc/built-in-macros/_drc_cop_integration.rb
@@ -476,7 +476,7 @@ module DRC
 
         layer.requires_region
 
-        res = DRCOpNode::new(self, RBA::CompoundRegionOperationNode::new_secondary(layer.data))
+        res = DRCOpNode::new(self) { RBA::CompoundRegionOperationNode::new_secondary(layer.data) }
         res.description = "secondary"
         return res
 
@@ -493,7 +493,7 @@ module DRC
     # is called on.
     
     def primary
-      res = DRCOpNode::new(self, RBA::CompoundRegionOperationNode::new_primary)
+      res = DRCOpNode::new(self) { RBA::CompoundRegionOperationNode::new_primary }
       res.description = "primary"
       return res
     end
@@ -520,7 +520,7 @@ module DRC
     # @/code
     
     def foreign
-      res = DRCOpNode::new(self, RBA::CompoundRegionOperationNode::new_foreign)
+      res = DRCOpNode::new(self) { RBA::CompoundRegionOperationNode::new_foreign }
       res.description = "foreign"
       return res
     end
@@ -1555,10 +1555,12 @@ CODE
 
     def _make_node(arg)
       if arg.is_a?(DRCLayer)
-        arg = DRCOpNode::new(self, RBA::CompoundRegionOperationNode::new_secondary(arg.data))
-        arg.description = "secondary"
+        node = DRCOpNode::new(self) { RBA::CompoundRegionOperationNode::new_secondary(arg.data) }
+        node.description = "secondary"
+        return node
+      else
+        return arg
       end
-      arg
     end
 
   end
diff --git a/src/drc/drc/built-in-macros/_drc_engine.rb b/src/drc/drc/built-in-macros/_drc_engine.rb
index fc024aa13..9a873be62 100644
--- a/src/drc/drc/built-in-macros/_drc_engine.rb
+++ b/src/drc/drc/built-in-macros/_drc_engine.rb
@@ -29,6 +29,8 @@ module DRC
 
       cv = RBA::CellView::active
 
+      @time = Time::now
+      @force_gc = ($drc_force_gc == true)   # for testing, $drc_force_gc can be set to true
       @generator = ""
       @rdb_index = nil
       @l2ndb_index = nil
@@ -73,6 +75,11 @@ module DRC
 
     end
 
+    # for testing
+    def force_gc(f)
+      @force_gc = f
+    end
+
     def both
       DRCBothEdges::new
     end
@@ -2137,7 +2144,10 @@ CODE
       t = RBA::Timer::new
       t.start
       self._process_events
-      GC.start # force a garbage collection before the operation to free unused memory
+      if @force_gc || Time::now - @time > 0.5
+        GC.start    # force a garbage collection before the operation to free unused memory
+        @time = Time::now
+      end
       res = yield
       t.stop
 
diff --git a/src/drc/drc/built-in-macros/_drc_layer.rb b/src/drc/drc/built-in-macros/_drc_layer.rb
index 8e3c13d69..abea2dd64 100644
--- a/src/drc/drc/built-in-macros/_drc_layer.rb
+++ b/src/drc/drc/built-in-macros/_drc_layer.rb
@@ -4250,11 +4250,13 @@ CODE
       tp.output("res", res)
       tp.input("input", self.data)
       tp.threads = (@engine.threads || 1)
+
       if tile_boundary
-        tp.input("boundary", tile_boundary.data)
+        boundary = tile_boundary.data
       else
-        tp.input("boundary", RBA::Region::new(self.data.bbox))
+        boundary = RBA::Region::new(self.data.bbox)
       end
+      tp.input("boundary", boundary)
 
       tp.var("vmin", limits[0] || 0.0)
       tp.var("vmax", limits[1] || 1.0)
diff --git a/src/drc/unit_tests/drcBasicTests.cc b/src/drc/unit_tests/drcBasicTests.cc
index 3e2adf02d..ea8917a0b 100644
--- a/src/drc/unit_tests/drcBasicTests.cc
+++ b/src/drc/unit_tests/drcBasicTests.cc
@@ -36,6 +36,7 @@ TEST(1)
 
   lym::Macro drc;
   drc.set_text (tl::sprintf (
+      "force_gc true\n"
       "source('%s', \"TOP\")\n"
       "target('%s', \"TOP\")\n"
       "l1 = input(1, 0)\n"
@@ -70,6 +71,7 @@ TEST(2)
 {
   lym::Macro drc;
   drc.set_text (
+    "force_gc true\n"
     "dbu 0.001\n"
     "def compare(a, b, ex)\n"
     "  a = a.to_s\n"
diff --git a/src/drc/unit_tests/drcGenericTests.cc b/src/drc/unit_tests/drcGenericTests.cc
index 10eccd418..ca6ac8d5f 100644
--- a/src/drc/unit_tests/drcGenericTests.cc
+++ b/src/drc/unit_tests/drcGenericTests.cc
@@ -30,6 +30,8 @@
 
 static void run_test (tl::TestBase *_this, const std::string &number, bool deep)
 {
+  std::string force_gc = "true";
+
   std::string rs = tl::testdata ();
   rs += "/drc/drcGenericTests_" + number + ".drc";
 
@@ -45,10 +47,11 @@ static void run_test (tl::TestBase *_this, const std::string &number, bool deep)
     //  Set some variables
     lym::Macro config;
     config.set_text (tl::sprintf (
+        "$drc_force_gc = %s\n"
         "$drc_test_source = '%s'\n"
         "$drc_test_target = '%s'\n"
         "$drc_test_deep = %s\n"
-      , input, output, deep ? "true" : "false")
+      , force_gc, input, output, deep ? "true" : "false")
     );
     config.set_interpreter (lym::Macro::Ruby);
     EXPECT_EQ (config.run (), 0);
diff --git a/src/drc/unit_tests/drcSimpleTests.cc b/src/drc/unit_tests/drcSimpleTests.cc
index c3969acbe..7ba20d07b 100644
--- a/src/drc/unit_tests/drcSimpleTests.cc
+++ b/src/drc/unit_tests/drcSimpleTests.cc
@@ -42,6 +42,7 @@ TEST(1)
     //  Set some variables
     lym::Macro config;
     config.set_text (tl::sprintf (
+        "$drc_force_gc = true\n"
         "$drc_test_source = nil\n"
         "$drc_test_target = '%s'\n"
       , output)
@@ -82,6 +83,7 @@ TEST(2)
     //  Set some variables
     lym::Macro config;
     config.set_text (tl::sprintf (
+        "$drc_force_gc = true\n"
         "$drc_test_source = '%s'\n"
         "$drc_test_target = '%s'\n"
       , input, output)
@@ -122,6 +124,7 @@ TEST(3_Flat)
     //  Set some variables
     lym::Macro config;
     config.set_text (tl::sprintf (
+        "$drc_force_gc = true\n"
         "$drc_test_source = '%s'\n"
         "$drc_test_target = '%s'\n"
       , input, output)
@@ -162,6 +165,7 @@ TEST(4_Hierarchical)
     //  Set some variables
     lym::Macro config;
     config.set_text (tl::sprintf (
+        "$drc_force_gc = true\n"
         "$drc_test_source = '%s'\n"
         "$drc_test_target = '%s'\n"
       , input, output)
@@ -202,6 +206,7 @@ TEST(5_FlatAntenna)
     //  Set some variables
     lym::Macro config;
     config.set_text (tl::sprintf (
+        "$drc_force_gc = true\n"
         "$drc_test_source = '%s'\n"
         "$drc_test_target = '%s'\n"
       , input, output)
@@ -242,6 +247,7 @@ TEST(5_FlatAntennaIncremental)
     //  Set some variables
     lym::Macro config;
     config.set_text (tl::sprintf (
+        "$drc_force_gc = true\n"
         "$drc_test_source = '%s'\n"
         "$drc_test_target = '%s'\n"
       , input, output)
@@ -282,6 +288,7 @@ TEST(6_HierarchicalAntenna)
     //  Set some variables
     lym::Macro config;
     config.set_text (tl::sprintf (
+        "$drc_force_gc = true\n"
         "$drc_test_source = '%s'\n"
         "$drc_test_target = '%s'\n"
       , input, output)
@@ -322,6 +329,7 @@ TEST(7_AntennaWithDiodes)
     //  Set some variables
     lym::Macro config;
     config.set_text (tl::sprintf (
+        "$drc_force_gc = true\n"
         "$drc_test_source = '%s'\n"
         "$drc_test_target = '%s'\n"
       , input, output)
@@ -362,6 +370,7 @@ TEST(8_TextsAndPolygons)
     //  Set some variables
     lym::Macro config;
     config.set_text (tl::sprintf (
+        "$drc_force_gc = true\n"
         "$drc_test_source = '%s'\n"
         "$drc_test_target = '%s'\n"
       , input, output)
@@ -427,6 +436,7 @@ TEST(9_NetlistExtraction)
     //  Set some variables
     lym::Macro config;
     config.set_text (tl::sprintf (
+        "$drc_force_gc = true\n"
         "$drc_test_source = '%s'\n"
         "$drc_test_target = '%s'\n"
         "$drc_test_target_simplified = '%s'\n"
@@ -471,6 +481,7 @@ TEST(10_NetlistExtractionFlat)
     //  Set some variables
     lym::Macro config;
     config.set_text (tl::sprintf (
+        "$drc_force_gc = true\n"
         "$drc_test_source = '%s'\n"
         "$drc_test_target = '%s'\n"
         "$drc_test_target_simplified = '%s'\n"
@@ -515,6 +526,7 @@ TEST(11_CustomDevices)
     //  Set some variables
     lym::Macro config;
     config.set_text (tl::sprintf (
+        "$drc_force_gc = true\n"
         "$drc_test_source = '%s'\n"
         "$drc_test_target = '%s'\n"
         "$drc_test_target_simplified = '%s'\n"
@@ -555,6 +567,7 @@ TEST(12_NetlistJoinLabels)
     //  Set some variables
     lym::Macro config;
     config.set_text (tl::sprintf (
+        "$drc_force_gc = true\n"
         "$drc_test_source = '%s'\n"
         "$drc_test_target = '%s'\n"
         "$drc_test_target_simplified = nil\n"
@@ -591,6 +604,7 @@ TEST(13a_KissingCorners)
     //  Set some variables
     lym::Macro config;
     config.set_text (tl::sprintf (
+        "$drc_force_gc = true\n"
         "$drc_test_source = '%s'\n"
         "$drc_test_target = '%s'\n"
       , input, output)
@@ -634,6 +648,7 @@ TEST(13b_KissingCornersDeep)
     //  Set some variables
     lym::Macro config;
     config.set_text (tl::sprintf (
+        "$drc_force_gc = true\n"
         "$drc_test_source = '%s'\n"
         "$drc_test_target = '%s'\n"
       , input, output)
@@ -681,6 +696,7 @@ TEST(14_SwitchingTargets)
     //  Set some variables
     lym::Macro config;
     config.set_text (tl::sprintf (
+        "$drc_force_gc = true\n"
         "$drc_test_source = '%s'\n"
         "$drc_test_target = '%s'\n"
         "$drc_test_target2 = '%s'\n"
@@ -732,6 +748,7 @@ TEST(15_issue548)
     //  Set some variables
     lym::Macro config;
     config.set_text (tl::sprintf (
+        "$drc_force_gc = true\n"
         "$drc_test_source = '%s'\n"
         "$drc_test_target = '%s'\n"
       , input, output)
@@ -773,6 +790,7 @@ TEST(16_issue570)
     //  Set some variables
     lym::Macro config;
     config.set_text (tl::sprintf (
+        "$drc_force_gc = true\n"
         "$drc_test_source = '%s'\n"
         "$drc_test_target = '%s'\n"
       , input, output)
@@ -814,6 +832,7 @@ TEST(17_issue570)
     //  Set some variables
     lym::Macro config;
     config.set_text (tl::sprintf (
+        "$drc_force_gc = true\n"
         "$drc_test_source = '%s'\n"
         "$drc_test_target = '%s'\n"
       , input, output)
@@ -854,6 +873,7 @@ TEST(18_forget)
     //  Set some variables
     lym::Macro config;
     config.set_text (tl::sprintf (
+        "$drc_force_gc = true\n"
         "$drc_test_source = '%s'\n"
         "$drc_test_target = '%s'\n"
       , input, output)
@@ -894,6 +914,7 @@ TEST(19_shielding)
     //  Set some variables
     lym::Macro config;
     config.set_text (tl::sprintf (
+        "$drc_force_gc = true\n"
         "$drc_test_source = '%s'\n"
         "$drc_test_target = '%s'\n"
       , input, output)
@@ -934,6 +955,7 @@ TEST(20_interact_with_count)
     //  Set some variables
     lym::Macro config;
     config.set_text (tl::sprintf (
+        "$drc_force_gc = true\n"
         "$drc_test_source = '%s'\n"
         "$drc_test_target = '%s'\n"
       , input, output)
@@ -974,6 +996,7 @@ TEST(21_breaking)
     //  Set some variables
     lym::Macro config;
     config.set_text (tl::sprintf (
+        "$drc_force_gc = true\n"
         "$drc_test_source = '%s'\n"
         "$drc_test_target = '%s'\n"
       , input, output)
@@ -1014,6 +1037,7 @@ TEST(22_opposite_filter)
     //  Set some variables
     lym::Macro config;
     config.set_text (tl::sprintf (
+        "$drc_force_gc = true\n"
         "$drc_test_source = '%s'\n"
         "$drc_test_target = '%s'\n"
       , input, output)
@@ -1054,6 +1078,7 @@ TEST(23_rect_filter)
     //  Set some variables
     lym::Macro config;
     config.set_text (tl::sprintf (
+        "$drc_force_gc = true\n"
         "$drc_test_source = '%s'\n"
         "$drc_test_target = '%s'\n"
       , input, output)
@@ -1094,6 +1119,7 @@ TEST(24_enclosing)
     //  Set some variables
     lym::Macro config;
     config.set_text (tl::sprintf (
+        "$drc_force_gc = true\n"
         "$drc_test_source = '%s'\n"
         "$drc_test_target = '%s'\n"
       , input, output)
@@ -1119,6 +1145,8 @@ TEST(24_enclosing)
 
 static void run_test (tl::TestBase *_this, const std::string &number, bool deep, bool oasis = false)
 {
+  std::string force_gc = "true";
+
   std::string rs = tl::testdata ();
   rs += "/drc/drcSimpleTests_" + number + ".drc";
 
@@ -1134,10 +1162,11 @@ static void run_test (tl::TestBase *_this, const std::string &number, bool deep,
     //  Set some variables
     lym::Macro config;
     config.set_text (tl::sprintf (
+        "$drc_force_gc = '%s'\n"
         "$drc_test_source = '%s'\n"
         "$drc_test_target = '%s'\n"
         "$drc_test_deep = %s\n"
-      , input, output, deep ? "true" : "false")
+      , force_gc, input, output, deep ? "true" : "false")
     );
     config.set_interpreter (lym::Macro::Ruby);
     EXPECT_EQ (config.run (), 0);
diff --git a/src/drc/unit_tests/drcSuiteTests.cc b/src/drc/unit_tests/drcSuiteTests.cc
index 3cfde1b3d..a329905e2 100644
--- a/src/drc/unit_tests/drcSuiteTests.cc
+++ b/src/drc/unit_tests/drcSuiteTests.cc
@@ -27,6 +27,8 @@
 
 void runtest (tl::TestBase *_this, int mode)
 {
+  std::string force_gc = "true";
+
   std::string rs = tl::testdata ();
   rs += "/drc/drcSuiteTests.drc";
 
@@ -44,10 +46,11 @@ void runtest (tl::TestBase *_this, int mode)
     //  Set some variables
     lym::Macro config;
     config.set_text (tl::sprintf (
+        "$drc_force_gc = %s\n"
         "$drc_test_source = '%s'\n"
         "$drc_test_target = '%s'\n"
         "$drc_test_mode = %d\n"
-      , input, output, mode)
+      , force_gc, input, output, mode)
     );
     config.set_interpreter (lym::Macro::Ruby);
     EXPECT_EQ (config.run (), 0);
diff --git a/src/lvs/unit_tests/lvsBasicTests.cc b/src/lvs/unit_tests/lvsBasicTests.cc
index 1b8492d94..175f3bb51 100644
--- a/src/lvs/unit_tests/lvsBasicTests.cc
+++ b/src/lvs/unit_tests/lvsBasicTests.cc
@@ -40,6 +40,8 @@ TEST(1)
 
   lym::Macro lvs;
   lvs.set_text (tl::sprintf (
+      "$drc_force_gc = true\n"
+      "\n"
       "source('%s', 'INVERTER')\n"
       "\n"
       "deep\n"
diff --git a/src/lvs/unit_tests/lvsSimpleTests.cc b/src/lvs/unit_tests/lvsSimpleTests.cc
index df95beedc..883eabf18 100644
--- a/src/lvs/unit_tests/lvsSimpleTests.cc
+++ b/src/lvs/unit_tests/lvsSimpleTests.cc
@@ -53,6 +53,7 @@ void run_test (tl::TestBase *_this, const std::string &suffix, const std::string
     //  Set some variables
     lym::Macro config;
     config.set_text (tl::sprintf (
+        "$drc_force_gc = true\n"
         "$lvs_test_source = '%s'\n"
         "$lvs_test_target_lvsdb = '%s'\n"
         "$lvs_test_target_cir = '%s'\n"
diff --git a/src/lvs/unit_tests/lvsTests.cc b/src/lvs/unit_tests/lvsTests.cc
index 5475484bd..989124420 100644
--- a/src/lvs/unit_tests/lvsTests.cc
+++ b/src/lvs/unit_tests/lvsTests.cc
@@ -47,6 +47,7 @@ void run_test (tl::TestBase *_this, const std::string &lvs_rs, const std::string
     //  Set some variables
     lym::Macro config;
     config.set_text (tl::sprintf (
+        "$drc_force_gc = true\n"
         "$lvs_test_source = '%s'\n"
         "$lvs_test_target_lvsdb = '%s'\n"
         "$lvs_test_target_cir = '%s'\n"
@@ -141,7 +142,7 @@ TEST(16_private)
 TEST(17_private)
 {
   test_is_long_runner ();
-  run_test (_this, "test_17.lylvs", "test_17b.cir.gz", "test_17.gds.gz", true, "test_17b_2.lvsdb");
+  run_test (_this, "test_17.lylvs", "test_17b.cir.gz", "test_17.gds.gz", true, "test_17b_3.lvsdb");
 }
 
 TEST(18_private)
@@ -159,7 +160,7 @@ TEST(19_private)
 TEST(20_private)
 {
   // test_is_long_runner ();
-  run_test (_this, "test_20.lylvs", "test_20.cir.gz", "test_20.gds.gz", true, "test_20b_2.lvsdb");
+  run_test (_this, "test_20.lylvs", "test_20.cir.gz", "test_20.gds.gz", true, "test_20b_3.lvsdb");
 }
 
 TEST(21_private)
diff --git a/src/rba/rba/rba.cc b/src/rba/rba/rba.cc
index c4099cc0a..2432f01d7 100644
--- a/src/rba/rba/rba.cc
+++ b/src/rba/rba/rba.cc
@@ -1001,6 +1001,10 @@ method_adaptor (int mid, int argc, VALUE *argv, VALUE self, bool ctor)
     const gsi::ClassBase *cls_decl;
     Proxy *p = 0;
 
+    //  this prevents side effects of callbacks raised from within the called functions -
+    //  if these trigger the GC, self is protected from destruction herein.
+    GCLocker gc_locker (self);
+
     if (TYPE (self) == T_CLASS) {
       //  we have a static method
       cls_decl = find_cclass (self);
diff --git a/src/rba/rba/rbaInternal.cc b/src/rba/rba/rbaInternal.cc
index bcec542b7..92b79e521 100644
--- a/src/rba/rba/rbaInternal.cc
+++ b/src/rba/rba/rbaInternal.cc
@@ -54,7 +54,7 @@ public:
   void mark_this ();
 
 private:
-  std::set<VALUE> m_objects;
+  std::map<VALUE, size_t> m_objects;
 
   static VALUE m_klass;
   static VALUE m_instance;
@@ -84,20 +84,31 @@ LockedObjectVault::~LockedObjectVault ()
 void
 LockedObjectVault::add (VALUE object)
 {
-  m_objects.insert (object);
+  auto i = m_objects.find (object);
+  if (i != m_objects.end ()) {
+    i->second += 1;
+  } else {
+    m_objects.insert (std::make_pair (object, size_t (1)));
+  }
 }
 
 void
 LockedObjectVault::remove (VALUE object)
 {
-  m_objects.erase (object);
+  auto i = m_objects.find (object);
+  if (i != m_objects.end ()) {
+    i->second -= 1;
+    if (i->second == 0) {
+      m_objects.erase (i);
+    }
+  }
 }
 
 void
 LockedObjectVault::mark_this ()
 {
-  for (std::set<VALUE>::iterator o = m_objects.begin (); o != m_objects.end (); ++o) {
-    rb_gc_mark (*o);
+  for (auto o = m_objects.begin (); o != m_objects.end (); ++o) {
+    rb_gc_mark (o->first);
   }
 }
 
@@ -158,90 +169,6 @@ gc_unlock_object (VALUE value)
   }
 }
 
-// --------------------------------------------------------------------------
-
-/**
- *  @brief A final finalizer
- *  Final destruction of finalized objects is delegated to this class.
- *  It's main purpose is to temporarily disable C++ destruction while
- *  in a callback. Deleting C++ objects in a callback leads to unpredictable
- *  side effects and must be avoided.
- */
-class InternalGC
-{
-public:
-  InternalGC ()
-    : m_enabled (true)
-  {
-    //  .. nothing yet ..
-  }
-
-  /**
-   *  @brief Enables or disables the GC
-   *  Returns the previous state
-   */
-  bool enable (bool e)
-  {
-    std::swap (e, m_enabled);
-    return e;
-  }
-
-  /**
-   *  @brief Queues (if disabled) or deletes the given object (plus all queued ones) if enabled
-   */
-  void destroy_maybe (const gsi::ClassBase *cls, void *obj)
-  {
-    if (! m_enabled) {
-      m_queue.push_back (std::make_pair (cls, obj));
-    } else {
-      m_queue.clear ();
-      cls->destroy (obj);
-      for (std::vector<std::pair<const gsi::ClassBase *, void *> >::const_iterator q = m_queue.begin (); q != m_queue.end (); ++q) {
-        q->first->destroy (q->second);
-      }
-    }
-  }
-
-private:
-  std::vector<std::pair<const gsi::ClassBase *, void *> > m_queue;
-  bool m_enabled;
-};
-
-static InternalGC s_gc;
-
-/**
- *  @brief Destroys the object through the internal GC
- */
-inline void destroy_object (const gsi::ClassBase *cls, void *obj)
-{
-  s_gc.destroy_maybe (cls, obj);
-}
-
-/**
- *  @brief A GC disabler
- *  By instantiating this object, the gc is disabled while the object is alive.
- *  Specifically in callbacks it's important to disable the GC to avoid undesired
- *  side effects.
- */
-class GCDisabler
-{
-public:
-  GCDisabler (InternalGC *gc = 0)
-    : mp_gc (gc ? gc : &s_gc)
-  {
-    m_was_enabled = mp_gc->enable (false);
-  }
-
-  ~GCDisabler()
-  {
-    mp_gc->enable (m_was_enabled);
-  }
-
-private:
-  bool m_was_enabled;
-  InternalGC *mp_gc;
-};
-
 // --------------------------------------------------------------------------
 //  Proxy implementation
 
@@ -309,8 +236,6 @@ bool Proxy::can_call () const
 void
 Proxy::call (int id, gsi::SerialArgs &args, gsi::SerialArgs &ret) const
 {
-  GCDisabler gc_disabler;
-
   tl_assert (id < int (m_cbfuncs.size ()) && id >= 0);
 
   const gsi::MethodBase *meth = m_cbfuncs [id].method;
@@ -635,7 +560,7 @@ Proxy::set (void *obj, bool owned, bool const_ref, bool can_destroy, VALUE self)
       //  Destroy the object if we are owner. We don't destroy the object if it was locked
       //  (either because we are not owner or from C++ side using keep())
       if (prev_owned) {
-        destroy_object (cls, prev_obj);
+        cls->destroy (prev_obj);
       }
 
     }
@@ -891,8 +816,6 @@ SignalHandler::define_class (VALUE module, const char *name)
 
 void SignalHandler::call (const gsi::MethodBase *meth, gsi::SerialArgs &args, gsi::SerialArgs &ret) const
 {
-  GCDisabler gc_disabler;
-
   VALUE argv = rb_ary_new2 (long (std::distance (meth->begin_arguments (), meth->end_arguments ())));
   RB_GC_GUARD (argv);
 
diff --git a/src/rba/rba/rbaInternal.h b/src/rba/rba/rbaInternal.h
index ccad2275e..21949105e 100644
--- a/src/rba/rba/rbaInternal.h
+++ b/src/rba/rba/rbaInternal.h
@@ -251,6 +251,31 @@ void gc_lock_object (VALUE value);
  */
 void gc_unlock_object (VALUE value);
 
+/**
+ *  @brief A Locker for the object based on the RIIA pattern
+ */
+class GCLocker
+{
+public:
+  GCLocker (VALUE value)
+    : m_value (value)
+  {
+    gc_lock_object (m_value);
+  }
+
+  ~GCLocker ()
+  {
+    gc_unlock_object (m_value);
+  }
+
+private:
+  GCLocker ();
+  GCLocker (const GCLocker &other);
+  GCLocker &operator= (const GCLocker &other);
+
+  VALUE m_value;
+};
+
 /**
  *  @brief Makes the locked object vault required for gc_lock_object and gc_unlock_object
  *
diff --git a/testdata/lvs/test_22c.lvsdb.1 b/testdata/lvs/test_22c.lvsdb.1
index 6ee12b507..0e0b1750e 100644
--- a/testdata/lvs/test_22c.lvsdb.1
+++ b/testdata/lvs/test_22c.lvsdb.1
@@ -31,11 +31,11 @@ layout(
  layer(l25)
  layer(l26)
  layer(l27)
- layer(l1)
+ layer(l22)
  layer(l2)
  layer(l4)
  layer(l6)
- layer(l22)
+ layer(l1)
 
  # Mask layer connectivity
  connect(l5 l5 l4)
@@ -54,21 +54,21 @@ layout(
  connect(l17 l18 l17 l26 l27)
  connect(l20 l20 l19)
  connect(l19 l20 l19 l27)
- connect(l21 l9 l21 l2 l22)
+ connect(l21 l9 l21 l22 l2)
  connect(l23 l9 l11 l23)
  connect(l24 l11 l13 l24)
  connect(l25 l13 l15 l25)
  connect(l26 l15 l17 l26)
  connect(l27 l17 l19 l27)
- connect(l1 l1)
+ connect(l22 l21 l22)
  connect(l2 l3 l21 l2 l4 l6)
  connect(l4 l5 l2 l4)
  connect(l6 l2 l6)
- connect(l22 l21 l22)
+ connect(l1 l1)
 
  # Global nets and connectivity
- global(l1 vss)
  global(l6 vss)
+ global(l1 vss)
 
  # Device class section
  class(active_res RES)
@@ -193,22 +193,22 @@ layout(
    rect(l21 (-170 80) (170 170))
    rect(l21 (-170 1070) (170 170))
    rect(l21 (-5 -1010) (170 170))
-   polygon(l2 (-465 -1120) (0 340) (-105 0) (0 420) (525 0) (0 -760))
-   rect(l2 (-525 1670) (445 420))
-   rect(l22 (-125 -1190) (330 270))
+   rect(l22 (-250 -220) (330 270))
    rect(l22 (950 -960) (150 2010))
    rect(l22 (-1100 -1320) (950 150))
+   polygon(l2 (-1495 -1050) (0 340) (-105 0) (0 420) (525 0) (0 -760))
+   rect(l2 (-525 1670) (445 420))
   )
   net(4
    polygon(l9 (1485 760) (0 840) (-245 0) (0 170) (245 0) (0 560) (170 0) (0 -1570))
    rect(l21 (-170 80) (170 170))
    rect(l21 (-170 1070) (170 170))
    rect(l21 (-335 -650) (170 170))
-   polygon(l2 (-125 -1480) (0 760) (525 0) (0 -420) (-105 0) (0 -340))
-   rect(l2 (-340 1670) (445 420))
-   rect(l22 (-650 -830) (330 270))
+   rect(l22 (-250 -220) (330 270))
    rect(l22 (-1280 -150) (950 150))
    rect(l22 (-1100 -1320) (150 2010))
+   polygon(l2 (1075 -2220) (0 760) (525 0) (0 -420) (-105 0) (0 -340))
+   rect(l2 (-340 1670) (445 420))
   )
   net(5 name(vdd)
    rect(l5 (-385 1780) (2950 1300))
diff --git a/testdata/lvs/test_22c.lvsdb.2 b/testdata/lvs/test_22c.lvsdb.2
index a3bacb5a7..4e5c37050 100644
--- a/testdata/lvs/test_22c.lvsdb.2
+++ b/testdata/lvs/test_22c.lvsdb.2
@@ -31,11 +31,11 @@ layout(
  layer(l25)
  layer(l26)
  layer(l27)
- layer(l1)
+ layer(l22)
  layer(l2)
  layer(l4)
  layer(l6)
- layer(l22)
+ layer(l1)
 
  # Mask layer connectivity
  connect(l5 l5 l4)
@@ -54,21 +54,21 @@ layout(
  connect(l17 l18 l17 l26 l27)
  connect(l20 l20 l19)
  connect(l19 l20 l19 l27)
- connect(l21 l9 l21 l2 l22)
+ connect(l21 l9 l21 l22 l2)
  connect(l23 l9 l11 l23)
  connect(l24 l11 l13 l24)
  connect(l25 l13 l15 l25)
  connect(l26 l15 l17 l26)
  connect(l27 l17 l19 l27)
- connect(l1 l1)
+ connect(l22 l21 l22)
  connect(l2 l3 l21 l2 l4 l6)
  connect(l4 l5 l2 l4)
  connect(l6 l2 l6)
- connect(l22 l21 l22)
+ connect(l1 l1)
 
  # Global nets and connectivity
- global(l1 vss)
  global(l6 vss)
+ global(l1 vss)
 
  # Device class section
  class(active_res RES)
@@ -193,22 +193,22 @@ layout(
    rect(l21 (-170 80) (170 170))
    rect(l21 (-170 1070) (170 170))
    rect(l21 (-5 -1010) (170 170))
-   polygon(l2 (-465 -1120) (0 340) (-105 0) (0 420) (525 0) (0 -760))
-   rect(l2 (-525 1670) (445 420))
-   rect(l22 (-125 -1190) (330 270))
+   rect(l22 (-250 -220) (330 270))
    rect(l22 (950 -960) (150 2010))
    rect(l22 (-1100 -1320) (950 150))
+   polygon(l2 (-1495 -1050) (0 340) (-105 0) (0 420) (525 0) (0 -760))
+   rect(l2 (-525 1670) (445 420))
   )
   net(4
    polygon(l9 (1485 760) (0 840) (-245 0) (0 170) (245 0) (0 560) (170 0) (0 -1570))
    rect(l21 (-170 80) (170 170))
    rect(l21 (-170 1070) (170 170))
    rect(l21 (-335 -650) (170 170))
-   polygon(l2 (-125 -1480) (0 760) (525 0) (0 -420) (-105 0) (0 -340))
-   rect(l2 (-340 1670) (445 420))
-   rect(l22 (-650 -830) (330 270))
+   rect(l22 (-250 -220) (330 270))
    rect(l22 (-1280 -150) (950 150))
    rect(l22 (-1100 -1320) (150 2010))
+   polygon(l2 (1075 -2220) (0 760) (525 0) (0 -420) (-105 0) (0 -340))
+   rect(l2 (-340 1670) (445 420))
   )
   net(5 name(vdd)
    rect(l5 (-385 1780) (2950 1300))
diff --git a/testdata/lvs/test_22d.lvsdb.1 b/testdata/lvs/test_22d.lvsdb.1
index 3c52f6e73..4f171845c 100644
--- a/testdata/lvs/test_22d.lvsdb.1
+++ b/testdata/lvs/test_22d.lvsdb.1
@@ -31,11 +31,11 @@ layout(
  layer(l25)
  layer(l26)
  layer(l27)
- layer(l1)
+ layer(l22)
  layer(l2)
  layer(l4)
  layer(l6)
- layer(l22)
+ layer(l1)
 
  # Mask layer connectivity
  connect(l5 l5 l4)
@@ -54,21 +54,21 @@ layout(
  connect(l17 l18 l17 l26 l27)
  connect(l20 l20 l19)
  connect(l19 l20 l19 l27)
- connect(l21 l9 l21 l2 l22)
+ connect(l21 l9 l21 l22 l2)
  connect(l23 l9 l11 l23)
  connect(l24 l11 l13 l24)
  connect(l25 l13 l15 l25)
  connect(l26 l15 l17 l26)
  connect(l27 l17 l19 l27)
- connect(l1 l1)
+ connect(l22 l21 l22)
  connect(l2 l3 l21 l2 l4 l6)
  connect(l4 l5 l2 l4)
  connect(l6 l2 l6)
- connect(l22 l21 l22)
+ connect(l1 l1)
 
  # Global nets and connectivity
- global(l1 vss)
  global(l6 vss)
+ global(l1 vss)
 
  # Device class section
  class(active_res RES)
@@ -193,22 +193,22 @@ layout(
    rect(l21 (-170 80) (170 170))
    rect(l21 (-170 1070) (170 170))
    rect(l21 (-5 -1010) (170 170))
-   polygon(l2 (-465 -1120) (0 340) (-105 0) (0 420) (525 0) (0 -760))
-   rect(l2 (-525 1670) (445 420))
-   rect(l22 (-125 -1190) (330 270))
+   rect(l22 (-250 -220) (330 270))
    rect(l22 (950 -960) (150 2010))
    rect(l22 (-1100 -1320) (950 150))
+   polygon(l2 (-1495 -1050) (0 340) (-105 0) (0 420) (525 0) (0 -760))
+   rect(l2 (-525 1670) (445 420))
   )
   net(4
    polygon(l9 (1485 760) (0 840) (-245 0) (0 170) (245 0) (0 560) (170 0) (0 -1570))
    rect(l21 (-170 80) (170 170))
    rect(l21 (-170 1070) (170 170))
    rect(l21 (-335 -650) (170 170))
-   polygon(l2 (-125 -1480) (0 760) (525 0) (0 -420) (-105 0) (0 -340))
-   rect(l2 (-340 1670) (445 420))
-   rect(l22 (-650 -830) (330 270))
+   rect(l22 (-250 -220) (330 270))
    rect(l22 (-1280 -150) (950 150))
    rect(l22 (-1100 -1320) (150 2010))
+   polygon(l2 (1075 -2220) (0 760) (525 0) (0 -420) (-105 0) (0 -340))
+   rect(l2 (-340 1670) (445 420))
   )
   net(5 name(vdd)
    rect(l5 (-385 1780) (2950 1300))
diff --git a/testdata/lvs/test_22d.lvsdb.2 b/testdata/lvs/test_22d.lvsdb.2
index 24c24136c..3a3bd09c8 100644
--- a/testdata/lvs/test_22d.lvsdb.2
+++ b/testdata/lvs/test_22d.lvsdb.2
@@ -31,11 +31,11 @@ layout(
  layer(l25)
  layer(l26)
  layer(l27)
- layer(l1)
+ layer(l22)
  layer(l2)
  layer(l4)
  layer(l6)
- layer(l22)
+ layer(l1)
 
  # Mask layer connectivity
  connect(l5 l5 l4)
@@ -54,21 +54,21 @@ layout(
  connect(l17 l18 l17 l26 l27)
  connect(l20 l20 l19)
  connect(l19 l20 l19 l27)
- connect(l21 l9 l21 l2 l22)
+ connect(l21 l9 l21 l22 l2)
  connect(l23 l9 l11 l23)
  connect(l24 l11 l13 l24)
  connect(l25 l13 l15 l25)
  connect(l26 l15 l17 l26)
  connect(l27 l17 l19 l27)
- connect(l1 l1)
+ connect(l22 l21 l22)
  connect(l2 l3 l21 l2 l4 l6)
  connect(l4 l5 l2 l4)
  connect(l6 l2 l6)
- connect(l22 l21 l22)
+ connect(l1 l1)
 
  # Global nets and connectivity
- global(l1 vss)
  global(l6 vss)
+ global(l1 vss)
 
  # Device class section
  class(active_res RES)
@@ -193,22 +193,22 @@ layout(
    rect(l21 (-170 80) (170 170))
    rect(l21 (-170 1070) (170 170))
    rect(l21 (-5 -1010) (170 170))
-   polygon(l2 (-465 -1120) (0 340) (-105 0) (0 420) (525 0) (0 -760))
-   rect(l2 (-525 1670) (445 420))
-   rect(l22 (-125 -1190) (330 270))
+   rect(l22 (-250 -220) (330 270))
    rect(l22 (950 -960) (150 2010))
    rect(l22 (-1100 -1320) (950 150))
+   polygon(l2 (-1495 -1050) (0 340) (-105 0) (0 420) (525 0) (0 -760))
+   rect(l2 (-525 1670) (445 420))
   )
   net(4
    polygon(l9 (1485 760) (0 840) (-245 0) (0 170) (245 0) (0 560) (170 0) (0 -1570))
    rect(l21 (-170 80) (170 170))
    rect(l21 (-170 1070) (170 170))
    rect(l21 (-335 -650) (170 170))
-   polygon(l2 (-125 -1480) (0 760) (525 0) (0 -420) (-105 0) (0 -340))
-   rect(l2 (-340 1670) (445 420))
-   rect(l22 (-650 -830) (330 270))
+   rect(l22 (-250 -220) (330 270))
    rect(l22 (-1280 -150) (950 150))
    rect(l22 (-1100 -1320) (150 2010))
+   polygon(l2 (1075 -2220) (0 760) (525 0) (0 -420) (-105 0) (0 -340))
+   rect(l2 (-340 1670) (445 420))
   )
   net(5 name(vdd)
    rect(l5 (-385 1780) (2950 1300))