fix [#32518] Vertex slide crash sometimes.

Undo would leave BMEditMesh->me pointer NULL, this would likely crash EDBM_verts_mirror_cache_begin() too.

Rather then restore 'me', remove the pointer altogether and use BMEditMesh->ob->data to save us having to keep track of 2 pointers.

4 files changed, 11 insertions, 9 deletions

diff --git a/source/blender/blenkernel/BKE_tessmesh.h b/source/blender/blenkernel/BKE_tessmesh.h
index 3a806651d61..dea5e726671 100644
--- a/source/blender/blenkernel/BKE_tessmesh.h
+++ b/source/blender/blenkernel/BKE_tessmesh.h
@@ -72,10 +72,12 @@ typedef struct BMEditMesh {
 	short selectmode;
 	short mat_nr;
 
-	/*Mesh structure this editmesh came from, if it came from one*/
-	struct Mesh *me;
+	/* Object this editmesh came from (if it came from one) */
 	struct Object *ob;
 
+	/* Unused for now, we could bring it back and assign in the same way 'ob' is */
+	// struct Mesh *me;
+
 	/*temp variables for x-mirror editing*/
 	int mirror_cdlayer; /* -1 is invalid */
 	int mirr_free_arrays;
diff --git a/source/blender/blenkernel/intern/editderivedmesh.c b/source/blender/blenkernel/intern/editderivedmesh.c
index 1577faccf40..befec1907da 100644
--- a/source/blender/blenkernel/intern/editderivedmesh.c
+++ b/source/blender/blenkernel/intern/editderivedmesh.c
@@ -1747,10 +1747,11 @@ DerivedMesh *getEditDerivedBMesh(BMEditMesh *em,
 BMEditMesh *BMEdit_FromObject(Object *ob)
 {
 	BLI_assert(ob->type == OB_MESH);
+	/* sanity check */
 #ifndef NDEBUG
-//	if (((Mesh *)ob->data)->edit_btmesh) {
-//		BLI_assert(((Mesh *)ob->data)->edit_btmesh->me == ob->data);
-//	}
+	if (((Mesh *)ob->data)->edit_btmesh) {
+		BLI_assert(((Mesh *)ob->data)->edit_btmesh->ob == ob);
+	}
 #endif
 	return ((Mesh *)ob->data)->edit_btmesh;
 }
diff --git a/source/blender/editors/mesh/editmesh_slide.c b/source/blender/editors/mesh/editmesh_slide.c
index 40c1ea7eff2..86ea5bc8651 100644
--- a/source/blender/editors/mesh/editmesh_slide.c
+++ b/source/blender/editors/mesh/editmesh_slide.c
@@ -208,7 +208,7 @@ static void vtx_slide_confirm(bContext *C, wmOperator *op)
 		other = BM_edge_other_vert(vso->sel_edge, vso->start_vtx);
 	}
 
-	if (em->me->editflag & ME_EDIT_MIRROR_X) {
+	if (((Mesh *)em->ob->data)->editflag & ME_EDIT_MIRROR_X) {
 		EDBM_verts_mirror_cache_begin(em, TRUE);
 
 		mirr_vtx = EDBM_verts_mirror_get(em, vso->start_vtx);
@@ -255,7 +255,7 @@ static void vtx_slide_confirm(bContext *C, wmOperator *op)
 		BM_select_history_store(em->bm, vso->start_vtx);
 	}
 
-	if (em->me->editflag & ME_EDIT_MIRROR_X) {
+	if (((Mesh *)em->ob->data)->editflag & ME_EDIT_MIRROR_X) {
 		EDBM_verts_mirror_cache_end(em);
 	}
 
diff --git a/source/blender/editors/mesh/editmesh_utils.c b/source/blender/editors/mesh/editmesh_utils.c
index 290ef3baba3..03e2f2691a8 100644
--- a/source/blender/editors/mesh/editmesh_utils.c
+++ b/source/blender/editors/mesh/editmesh_utils.c
@@ -345,7 +345,6 @@ void EDBM_mesh_make(ToolSettings *ts, Scene *UNUSED(scene), Object *ob)
 	me->edit_btmesh->selectmode = me->edit_btmesh->bm->selectmode = ts->selectmode;
 	me->edit_btmesh->mat_nr = (ob->actcol > 0) ? ob->actcol - 1 : 0;
 
-	me->edit_btmesh->me = me;
 	me->edit_btmesh->ob = ob;
 }
 
@@ -1056,7 +1055,7 @@ static BMVert *cache_mirr_intptr_as_bmvert(intptr_t *index_lookup, int index)
 #define BM_CD_LAYER_ID "__mirror_index"
 void EDBM_verts_mirror_cache_begin(BMEditMesh *em, const short use_select)
 {
-	Mesh *me = em->me;
+	Mesh *me = (Mesh *)em->ob->data;
 	BMesh *bm = em->bm;
 	BMIter iter;
 	BMVert *v;