fix for crash pasting nodes into a node tree when the ID pointer is lost.

also fix for ID user count on paste which wasn't increasing.

source/blender/blenkernel/BKE_node.h

@@ -388,6 +388,7 @@ void            nodeSocketSetType(struct bNodeSocket *sock, int type);
 /* Node Clipboard */
 void                   BKE_node_clipboard_init(struct bNodeTree *ntree);
 void                   BKE_node_clipboard_clear(void);
+int                    BKE_node_clipboard_validate(void);
 void                   BKE_node_clipboard_add_node(struct bNode *node);
 void                   BKE_node_clipboard_add_link(struct bNodeLink *link);
 const struct ListBase *BKE_node_clipboard_get_nodes(void);

source/blender/blenkernel/intern/node.c

@@ -1425,13 +1425,37 @@ void nodeSocketSetType(bNodeSocket *sock, int type)
 
 /* ************** Node Clipboard *********** */
 
+#define USE_NODE_CB_VALIDATE
+
+#ifdef USE_NODE_CB_VALIDATE
+/**
+ * This data structure is to validate the node on creation,
+ * otherwise we may reference missing data.
+ *
+ * Currently its only used for ID's, but nodes may one day
+ * referene other pointers which need validation.
+ */
+typedef struct bNodeClipboardExtraInfo {
+    struct bNodeClipboardExtraInfo *next, *prev;
+	ID  *id;
+    char id_name[MAX_ID_NAME];
+    char library_name[FILE_MAX];
+} bNodeClipboardExtraInfo;
+#endif  /* USE_NODE_CB_VALIDATE */
+
+
 typedef struct bNodeClipboard {
 	ListBase nodes;
+
+#ifdef USE_NODE_CB_VALIDATE
+    ListBase nodes_extra_info;
+#endif
+
 	ListBase links;
 	int type;
 } bNodeClipboard;
 
-bNodeClipboard node_clipboard;
+bNodeClipboard node_clipboard = {{0}};
 
 void BKE_node_clipboard_init(struct bNodeTree *ntree)
 {
@@ -1454,11 +1478,83 @@ void BKE_node_clipboard_clear(void)
 		nodeFreeNode(NULL, node);
 	}
 	node_clipboard.nodes.first = node_clipboard.nodes.last = NULL;
+
+#ifdef USE_NODE_CB_VALIDATE
+    BLI_freelistN(&node_clipboard.nodes_extra_info);
+#endif
+}
+
+/* return FALSE when one or more ID's are lost */
+int BKE_node_clipboard_validate(void)
+{
+	int ok = TRUE;
+
+#ifdef USE_NODE_CB_VALIDATE
+	bNodeClipboardExtraInfo *node_info;
+	bNode *node;
+
+
+	/* lists must be aligned */
+	BLI_assert(BLI_countlist(&node_clipboard.nodes) ==
+			   BLI_countlist(&node_clipboard.nodes_extra_info));
+
+	for (node = node_clipboard.nodes.first, node_info = node_clipboard.nodes_extra_info.first;
+		 node;
+		 node = node->next, node_info = node_info->next)
+	{
+		/* validate the node against the stored node info */
+
+		/* re-assign each loop since we may clear,
+		 * open a new file where the ID is valid, and paste again */
+		node->id = node_info->id;
+
+		/* currently only validate the ID */
+		if (node->id) {
+			ListBase *lb = which_libbase(G.main, GS(node_info->id_name));
+			BLI_assert(lb != NULL);
+
+			if (BLI_findindex(lb, node_info->id) == -1) {
+				/* may assign NULL */
+				node->id = BLI_findstring(lb, node_info->id_name + 2, offsetof(ID, name) + 2);
+				printf("%s %p\n", node_info->id_name, node->id);
+				if (node->id == NULL) {
+					ok = FALSE;
+				}
+			}
+		}
+	}
+#endif  /* USE_NODE_CB_VALIDATE */
+
+	return ok;
 }
 
 void BKE_node_clipboard_add_node(bNode *node)
 {
+#ifdef USE_NODE_CB_VALIDATE
+    /* add extra info */
+    bNodeClipboardExtraInfo *node_info = MEM_mallocN(sizeof(bNodeClipboardExtraInfo), STRINGIFY(bNodeClipboardExtraInfo));
+
+	node_info->id = node->id;
+    if (node->id) {
+        BLI_strncpy(node_info->id_name, node->id->name, sizeof(node_info->id_name));
+        if (node->id->lib) {
+            BLI_strncpy(node_info->library_name, node->id->lib->filepath, sizeof(node_info->library_name));
+        }
+        else {
+            node_info->library_name[0] = '\0';
+        }
+    }
+    else {
+        node_info->id_name[0] = '\0';
+        node_info->library_name[0] = '\0';
+    }
+    BLI_addtail(&node_clipboard.nodes_extra_info, node_info);
+	/* end extra info */
+#endif  /* USE_NODE_CB_VALIDATE */
+
+    /* add node */
 	BLI_addtail(&node_clipboard.nodes, node);
+
 }
 
 void BKE_node_clipboard_add_link(bNodeLink *link)

source/blender/editors/space_node/node_edit.c

@@ -2019,10 +2019,13 @@ static int node_clipboard_paste_exec(bContext *C, wmOperator *op)
 	bNodeTree *ntree = snode->edittree;
 	bNode *gnode = node_tree_get_editgroup(snode->nodetree);
 	float gnode_x = 0.0f, gnode_y = 0.0f;
+	const ListBase *clipboard_nodes_lb;
+	const ListBase *clipboard_links_lb;
 	bNode *node;
 	bNodeLink *link;
 	int num_nodes;
 	float centerx, centery;
+	int is_clipboard_valid;
 
 	if (BKE_node_clipboard_get_type() != ntree->type) {
 		BKE_report(op->reports, RPT_ERROR, "Clipboard nodes are an incompatible type");
@@ -2038,10 +2041,17 @@ static int node_clipboard_paste_exec(bContext *C, wmOperator *op)
 	if (gnode)
 		nodeToView(gnode, 0.0f, 0.0f, &gnode_x, &gnode_y);
 
+
+	/* validate pointers in the clipboard */
+	is_clipboard_valid = BKE_node_clipboard_validate();
+
+	clipboard_nodes_lb = BKE_node_clipboard_get_nodes();
+	clipboard_links_lb = BKE_node_clipboard_get_links();
+
 	/* calculate "barycenter" for placing on mouse cursor */
 	num_nodes = 0;
 	centerx = centery = 0.0f;
-	for (node = BKE_node_clipboard_get_nodes()->first; node; node = node->next) {
+	for (node = clipboard_nodes_lb->first; node; node = node->next) {
 		++num_nodes;
 		centerx += 0.5f * (node->totr.xmin + node->totr.xmax);
 		centery += 0.5f * (node->totr.ymin + node->totr.ymax);
@@ -2050,15 +2060,18 @@ static int node_clipboard_paste_exec(bContext *C, wmOperator *op)
 	centery /= num_nodes;
 
 	/* copy nodes from clipboard */
-	for (node = BKE_node_clipboard_get_nodes()->first; node; node = node->next) {
+	for (node = clipboard_nodes_lb->first; node; node = node->next) {
 		bNode *new_node = nodeCopyNode(ntree, node);
 
+		/* needed since nodeCopyNode() doesn't increase ID's */
+		id_us_plus(node->id);
+
 		/* pasted nodes are selected */
 		node_select(new_node);
 	}
 	
 	/* reparent copied nodes */
-	for (node = BKE_node_clipboard_get_nodes()->first; node; node = node->next) {
+	for (node = clipboard_nodes_lb->first; node; node = node->next) {
 		bNode *new_node = node->new_node;
 		if (new_node->parent)
 			new_node->parent = new_node->parent->new_node;
@@ -2071,7 +2084,7 @@ static int node_clipboard_paste_exec(bContext *C, wmOperator *op)
 		}
 	}
 
-	for (link = BKE_node_clipboard_get_links()->first; link; link = link->next) {
+	for (link = clipboard_links_lb->first; link; link = link->next) {
 		nodeAddLink(ntree, link->fromnode->new_node, link->fromsock->new_sock,
 		            link->tonode->new_node, link->tosock->new_sock);
 	}
@@ -2081,6 +2094,10 @@ static int node_clipboard_paste_exec(bContext *C, wmOperator *op)
 	snode_notify(C, snode);
 	snode_dag_update(C, snode);
 
+	if (is_clipboard_valid == FALSE) {
+		BKE_report(op->reports, RPT_ERROR, "Some nodes ID references could not be found");
+	}
+
 	return OPERATOR_FINISHED;
 }