Fix (unreported): unpredictable crashes when it is done snap after automerge.

The `em->tottri` of an evaluated object can be different from the actual amount of looptris.

1 files changed, 11 insertions, 6 deletions

diff --git a/source/blender/editors/transform/transform_snap_object.c b/source/blender/editors/transform/transform_snap_object.c
index c31019144b5..feca8f3f47a 100644
--- a/source/blender/editors/transform/transform_snap_object.c
+++ b/source/blender/editors/transform/transform_snap_object.c
@@ -564,13 +564,21 @@ static bool raycastEditMesh(
 	if (treedata->tree == NULL) {
 		BVHCache **bvh_cache = NULL;
 		BLI_bitmap *elem_mask = NULL;
+		BMEditMesh *em_orig;
 		int looptri_num_active = -1;
 
+		/* Get original version of the edit_btmesh. */
+		em_orig = BKE_editmesh_from_object(DEG_get_original_object(ob));
+
 		if (sctx->callbacks.edit_mesh.test_face_fn) {
-			elem_mask = BLI_BITMAP_NEW(em->tottri, __func__);
+			BMesh *bm = em_orig->bm;
+			BLI_assert(poly_to_tri_count(bm->totface, bm->totloop) == em_orig->tottri);
+
+			elem_mask = BLI_BITMAP_NEW(em_orig->tottri, __func__);
 			looptri_num_active = BM_iter_mesh_bitmap_from_filter_tessface(
-			        em->bm, elem_mask,
-			        sctx->callbacks.edit_mesh.test_face_fn, sctx->callbacks.edit_mesh.user_data);
+			        bm, elem_mask,
+			        sctx->callbacks.edit_mesh.test_face_fn,
+			        sctx->callbacks.edit_mesh.user_data);
 		}
 		else {
 			/* Only cache if bvhtree is created without a mask.
@@ -578,9 +586,6 @@ static bool raycastEditMesh(
 			bvh_cache = &em_bvh_cache;
 		}
 
-		/* Get original version of the edit_btmesh. */
-		BMEditMesh *em_orig = BKE_editmesh_from_object(DEG_get_original_object(ob));
-
 		bvhtree_from_editmesh_looptri_ex(
 		        treedata, em_orig, elem_mask, looptri_num_active,
 		        0.0f, 4, 6, bvh_cache);