From 79e529c5ec16d644693c1a71790819e020a293cd Mon Sep 17 00:00:00 2001
From: Brecht Van Lommel <brecht@blender.org>
Date: Wed, 27 May 2020 18:00:59 +0200
Subject: Fix T77109: Cycles viewport render crash after object add and undo

---
 intern/cycles/blender/blender_session.cpp | 4 ++++
 intern/cycles/blender/blender_sync.cpp    | 8 ++++++++
 intern/cycles/blender/blender_sync.h      | 2 ++
 3 files changed, 14 insertions(+)

(limited to 'intern/cycles')

diff --git a/intern/cycles/blender/blender_session.cpp b/intern/cycles/blender/blender_session.cpp
index 5ea96d6bdfd..ed90d054d73 100644
--- a/intern/cycles/blender/blender_session.cpp
+++ b/intern/cycles/blender/blender_session.cpp
@@ -168,9 +168,13 @@ void BlenderSession::create_session()
 
 void BlenderSession::reset_session(BL::BlendData &b_data, BL::Depsgraph &b_depsgraph)
 {
+  /* Update data, scene and depsgraph pointers. These can change after undo. */
   this->b_data = b_data;
   this->b_depsgraph = b_depsgraph;
   this->b_scene = b_depsgraph.scene_eval();
+  if (sync) {
+    sync->reset(this->b_data, this->b_scene);
+  }
 
   if (preview_osl) {
     PointerRNA cscene = RNA_pointer_get(&b_scene.ptr, "cycles");
diff --git a/intern/cycles/blender/blender_sync.cpp b/intern/cycles/blender/blender_sync.cpp
index e8031be7dd1..90736b7630d 100644
--- a/intern/cycles/blender/blender_sync.cpp
+++ b/intern/cycles/blender/blender_sync.cpp
@@ -78,6 +78,14 @@ BlenderSync::~BlenderSync()
 {
 }
 
+void BlenderSync::reset(BL::BlendData &b_data, BL::Scene &b_scene)
+{
+  /* Update data and scene pointers in case they change in session reset,
+   * for example after undo. */
+  this->b_data = b_data;
+  this->b_scene = b_scene;
+}
+
 /* Sync */
 
 void BlenderSync::sync_recalc(BL::Depsgraph &b_depsgraph, BL::SpaceView3D &b_v3d)
diff --git a/intern/cycles/blender/blender_sync.h b/intern/cycles/blender/blender_sync.h
index 650b4f5bb4e..f0ea5194c29 100644
--- a/intern/cycles/blender/blender_sync.h
+++ b/intern/cycles/blender/blender_sync.h
@@ -61,6 +61,8 @@ class BlenderSync {
               Progress &progress);
   ~BlenderSync();
 
+  void reset(BL::BlendData &b_data, BL::Scene &b_scene);
+
   /* sync */
   void sync_recalc(BL::Depsgraph &b_depsgraph, BL::SpaceView3D &b_v3d);
   void sync_data(BL::RenderSettings &b_render,
-- 
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