Index: trunk/src/board.c
===================================================================
--- trunk/src/board.c	(revision 12232)
+++ trunk/src/board.c	(revision 12233)
@@ -52,6 +52,7 @@
 	pcb_ratspatch_destroy(pcb);
 	pcb_data_free(pcb->Data);
 	free(pcb->Data);
+
 	/* release font symbols */
 	pcb_fontkit_free(&pcb->fontkit);
 	for (i = 0; i < PCB_NUM_NETLISTS; i++)
@@ -58,6 +59,9 @@
 		pcb_lib_free(&(pcb->NetlistLib[i]));
 	vtroutestyle_uninit(&pcb->RouteStyle);
 	pcb_attribute_free(&pcb->Attributes);
+
+	pcb_layergroup_free_stack(&pcb->LayerGroups);
+
 	/* clear struct */
 	memset(pcb, 0, sizeof(pcb_board_t));
 }
Index: trunk/src/layer_grp.c
===================================================================
--- trunk/src/layer_grp.c	(revision 12232)
+++ trunk/src/layer_grp.c	(revision 12233)
@@ -183,6 +183,12 @@
 	return pcb_true;
 }
 
+static int pcb_layergrp_free_fields(pcb_layergrp_t *g)
+{
+	free(g->name);
+}
+
+
 int pcb_layergrp_free(pcb_board_t *pcb, pcb_layergrp_id_t id)
 {
 	pcb_layer_stack_t *stack = &pcb->LayerGroups;
@@ -189,12 +195,11 @@
 	if ((id >= 0) && (id < stack->len)) {
 		int n;
 		pcb_layergrp_t *g = stack->grp + id;
-		if (g->name != NULL)
-			free(g->name);
 		for(n = 0; n < g->len; n++) {
 			pcb_layer_t *layer = pcb->Data->Layer + g->lid[n];
 			layer->meta.real.grp = -1;
 		}
+		pcb_layergrp_free_fields(g);
 		memset(g, 0, sizeof(pcb_layergrp_t));
 		return 0;
 	}
@@ -832,7 +837,18 @@
 	return 0;
 }
 
+void pcb_layergroup_free_stack(pcb_layer_stack_t *st)
+{
+	int n;
 
+	for(n = 0; n < st->len; n++)
+		pcb_layergrp_free_fields(st->grp + n);
+
+	free(st->cache.copper);
+	st->cache.copper = NULL;
+	st->cache.copper_len = st->cache.copper_alloced = 0;
+}
+
 static pcb_layergrp_id_t pcb_layergrp_get_cached(pcb_board_t *pcb, pcb_layer_id_t *cache, unsigned int loc, unsigned int typ)
 {
 	pcb_layergrp_t *g;
Index: trunk/src/layer_grp.h
===================================================================
--- trunk/src/layer_grp.h	(revision 12232)
+++ trunk/src/layer_grp.h	(revision 12233)
@@ -56,8 +56,15 @@
 struct pcb_layer_stack_s {
 	pcb_cardinal_t len;
 	pcb_layergrp_t grp[PCB_MAX_LAYERGRP];
+	struct { /* cache copper groups from top to bottom for fast padstack ("bbvia") lookup */
+		int copper_len, copper_alloced;
+		pcb_layergrp_id_t *copper;
+	} cache;
 };
 
+/* Free all fields of a layer stack */
+void pcb_layergroup_free_stack(pcb_layer_stack_t *st);
+
 /* Return the layer group for an id, or NULL on error (range check) */
 pcb_layergrp_t *pcb_get_layergrp(pcb_board_t *pcb, pcb_layergrp_id_t gid);