Fix T44439: outliner's treestore could keep invalid ID pointers, could crash on undo due to invalid mem access.

We cannot nuke treestore in readfile's `blo_lib_link_screen_restore()`, because this will
destroy all UI-state data (like opened/closed items, etc.).

Since we cannot know for sure whether an ID pointer from tselem->id is valid here, we
have to ensure they are never invalid, i.e. to always set them to NULL when we delete them.

To do so, this commit uses a similar approach as what already exists for ID references
in WM notifiers - it extends `free_notifier_reference_cb()` to also nullify those IDs in
all outliners.

Note that some ID types are not used(shown) by outliner currently, so `TREESTORE_ID_TYPE` macro
was added, that checks whether an ID is possibly used by outliner. Avoids a few searches
in whole tree whene deleting some IDs.

Reviewers: campbellbarton, sergey

Maniphest Tasks: T44439

Differential Revision: https://developer.blender.org/D1272

4 files changed, 81 insertions, 0 deletions

diff --git a/source/blender/editors/include/ED_outliner.h b/source/blender/editors/include/ED_outliner.h
new file mode 100644
index 00000000000..af4af8e2f5d
--- /dev/null
+++ b/source/blender/editors/include/ED_outliner.h
@@ -0,0 +1,36 @@
+/*
+ * ***** BEGIN GPL LICENSE BLOCK *****
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ * The Original Code is Copyright (C) 2015, Blender Foundation
+ *
+ * ***** END GPL LICENSE BLOCK *****
+ */
+
+/** \file ED_outliner.h
+ *  \ingroup editors
+ */
+
+#ifndef __ED_OUTLINER_H__
+#define __ED_OUTLINER_H__
+
+struct ID;
+struct SpaceOops;
+
+/* Used to check whether a given texture context is valid in current context. */
+void ED_outliner_id_unref(struct SpaceOops *so, const struct ID *id);
+
+#endif /*  __ED_OUTLINER_H__ */
diff --git a/source/blender/editors/space_outliner/outliner_edit.c b/source/blender/editors/space_outliner/outliner_edit.c
index 798dae2cef3..058b8c4de5a 100644
--- a/source/blender/editors/space_outliner/outliner_edit.c
+++ b/source/blender/editors/space_outliner/outliner_edit.c
@@ -39,20 +39,24 @@
 
 #include "BLI_blenlib.h"
 #include "BLI_utildefines.h"
+#include "BLI_mempool.h"
 
 #include "BLF_translation.h"
 
 #include "BKE_animsys.h"
 #include "BKE_context.h"
 #include "BKE_depsgraph.h"
+#include "BKE_global.h"
 #include "BKE_library.h"
 #include "BKE_main.h"
+#include "BKE_outliner_treehash.h"
 #include "BKE_report.h"
 #include "BKE_scene.h"
 #include "BKE_material.h"
 #include "BKE_group.h"
 
 #include "ED_object.h"
+#include "ED_outliner.h"
 #include "ED_screen.h"
 #include "ED_keyframing.h"
 
@@ -1952,3 +1956,35 @@ void OUTLINER_OT_group_link(wmOperatorType *ot)
 	/* properties */
 	RNA_def_string(ot->srna, "object", "Object", MAX_ID_NAME, "Object", "Target Object");
 }
+
+/******** Utils to clear any ref to freed ID... **********/
+
+void ED_outliner_id_unref(SpaceOops *so, const ID *id)
+{
+	/* Some early out checks. */
+	if (!TREESTORE_ID_TYPE(id)) {
+		return;  /* ID type is not used by outilner... */
+	}
+
+	if (so->search_tse.id == id) {
+		so->search_tse.id = NULL;
+	}
+
+	if (so->treestore) {
+		TreeStoreElem *tselem;
+		BLI_mempool_iter iter;
+		bool changed = false;
+
+		BLI_mempool_iternew(so->treestore, &iter);
+		while ((tselem = BLI_mempool_iterstep(&iter))) {
+			if (tselem->id == id) {
+				tselem->id = NULL;
+				changed = true;
+			}
+		}
+		if (so->treehash && changed) {
+			/* rebuild hash table, because it depends on ids too */
+			BKE_outliner_treehash_rebuild_from_treestore(so->treehash, so->treestore);
+		}
+	}
+}
diff --git a/source/blender/editors/space_outliner/outliner_intern.h b/source/blender/editors/space_outliner/outliner_intern.h
index b4b73a11a14..38672ef14dd 100644
--- a/source/blender/editors/space_outliner/outliner_intern.h
+++ b/source/blender/editors/space_outliner/outliner_intern.h
@@ -57,6 +57,10 @@ typedef struct TreeElement {
 	PointerRNA rnaptr;         // RNA Pointer
 }  TreeElement;
 
+#define TREESTORE_ID_TYPE(_id) \
+	(ELEM(GS((_id)->name), ID_SCE, ID_LI, ID_OB, ID_ME, ID_CU, ID_MB, ID_MA, ID_TE, ID_IM, ID_LT, ID_LA, ID_CA) || \
+	 ELEM(GS((_id)->name), ID_KE, ID_WO, ID_SPK, ID_GR, ID_AR, ID_AC, ID_BR, ID_PA, ID_GD, ID_LS))
+
 /* TreeElement->flag */
 #define TE_ACTIVE       1
 #define TE_ICONROW      2
diff --git a/source/blender/editors/space_outliner/outliner_tree.c b/source/blender/editors/space_outliner/outliner_tree.c
index 17a6e952ee1..4b07c400220 100644
--- a/source/blender/editors/space_outliner/outliner_tree.c
+++ b/source/blender/editors/space_outliner/outliner_tree.c
@@ -855,6 +855,11 @@ static TreeElement *outliner_add_element(SpaceOops *soops, ListBase *lb, void *i
 		return NULL;
 	}
 
+	if (type == 0) {
+		/* Zero type means real ID, ensure we do not get non-outliner ID types here... */
+		BLI_assert(TREESTORE_ID_TYPE(id));
+	}
+
 	te = MEM_callocN(sizeof(TreeElement), "tree elem");
 	/* add to the visual tree */
 	BLI_addtail(lb, te);