Fix T54098: Crash existing /w dyntopo sculpt

Optionally don't remap indices for objects.

Checking all objects parent's would reference a freed pointer
while freeing all objects.

In the case of dynamic topology there is no use in keeping track
of hook/vertex-parent indices.

Also disable this when creating meshes for undo storage
since adding an undo step shouldn't be modifying other objects.

3 files changed, 11 insertions, 2 deletions

diff --git a/source/blender/editors/mesh/editmesh_tools.c b/source/blender/editors/mesh/editmesh_tools.c
index 4b4f1b2afea..c979a73e964 100644
--- a/source/blender/editors/mesh/editmesh_tools.c
+++ b/source/blender/editors/mesh/editmesh_tools.c
@@ -3357,7 +3357,11 @@ static int edbm_separate_exec(bContext *C, wmOperator *op)
 					}
 
 					if (retval_iter) {
-						BM_mesh_bm_to_me(bm_old, me, (&(struct BMeshToMeshParams){0}));
+						BM_mesh_bm_to_me(
+						        bm_old, me,
+						        (&(struct BMeshToMeshParams){
+						            .calc_object_remap = true,
+						        }));
 
 						DAG_id_tag_update(&me->id, OB_RECALC_DATA);
 						WM_event_add_notifier(C, NC_GEOM | ND_DATA, me);
diff --git a/source/blender/editors/mesh/editmesh_undo.c b/source/blender/editors/mesh/editmesh_undo.c
index 534ca22178e..11667ed5710 100644
--- a/source/blender/editors/mesh/editmesh_undo.c
+++ b/source/blender/editors/mesh/editmesh_undo.c
@@ -496,6 +496,8 @@ static void *editbtMesh_to_undoMesh(void *emv, void *obdata)
 
 	BM_mesh_bm_to_me(
 	        em->bm, &um->me, (&(struct BMeshToMeshParams){
+	            /* Undo code should not be manipulating 'G.main->object' hooks/vertex-parent. */
+	            .calc_object_remap = false,
 	            .cd_mask_extra = CD_MASK_SHAPE_KEYINDEX,
 	        }));
 
diff --git a/source/blender/editors/mesh/editmesh_utils.c b/source/blender/editors/mesh/editmesh_utils.c
index e407d342603..c4440fa190a 100644
--- a/source/blender/editors/mesh/editmesh_utils.c
+++ b/source/blender/editors/mesh/editmesh_utils.c
@@ -380,7 +380,10 @@ void EDBM_mesh_load(Object *ob)
 		bm->shapenr = 1;
 	}
 
-	BM_mesh_bm_to_me(bm, me, (&(struct BMeshToMeshParams){0}));
+	BM_mesh_bm_to_me(
+	        bm, me, (&(struct BMeshToMeshParams){
+	            .calc_object_remap = true,
+	        }));
 
 #ifdef USE_TESSFACE_DEFAULT
 	BKE_mesh_tessface_calc(me);