fix [#36923] Merge / Delete vertices crashes for some meshes

add BM_ITER_MESH_MUTABLE which steps before entering the for() loop body and prevents the assert from complaining about removing mesh data while iterating as well as the crash.

this was done in quite a few areas, more may turn up.

1 files changed, 15 insertions, 0 deletions

diff --git a/source/blender/bmesh/intern/bmesh_iterators.h b/source/blender/bmesh/intern/bmesh_iterators.h
index bb25d3fabd1..fdf0f27f05f 100644
--- a/source/blender/bmesh/intern/bmesh_iterators.h
+++ b/source/blender/bmesh/intern/bmesh_iterators.h
@@ -89,6 +89,20 @@ extern const char bm_iter_itype_htype_map[BM_ITYPE_MAX];
 #define BM_ITER_MESH_INDEX(ele, iter, bm, itype, indexvar) \
 	for (ele = BM_iter_new(iter, bm, itype, NULL), indexvar = 0; ele; ele = BM_iter_step(iter), (indexvar)++)
 
+/* a version of BM_ITER_MESH which keeps the next item in storage
+ * so we can delete the current item, see bug [#36923] */
+#ifdef DEBUG
+#  define BM_ITER_MESH_MUTABLE(ele, ele_next, iter, bm, itype) \
+	for (ele = BM_iter_new(iter, bm, itype, NULL); \
+	ele ? ((void)((iter)->count = BM_iter_mesh_count(bm, itype)), \
+	       (void)(ele_next = BM_iter_step(iter)), 1) : 0; \
+	ele = ele_next)
+#else
+#  define BM_ITER_MESH_MUTABLE(ele, ele_next, iter, bm, itype) \
+	for (ele = BM_iter_new(iter, bm, itype, NULL); ele ? ((ele_next = BM_iter_step(iter)), 1) : 0; ele = ele_next)
+#endif
+
+
 #define BM_ITER_ELEM(ele, iter, data, itype) \
 	for (ele = BM_iter_new(iter, NULL, itype, data); ele; ele = BM_iter_step(iter))
 
@@ -182,6 +196,7 @@ typedef struct BMIter {
 	char itype;
 } BMIter;
 
+int     BM_iter_mesh_count(BMesh *bm, const char itype);
 void   *BM_iter_at_index(BMesh *bm, const char itype, void *data, int index) ATTR_WARN_UNUSED_RESULT;
 int     BM_iter_as_array(BMesh *bm, const char itype, void *data, void **array, const int len);
 void   *BM_iter_as_arrayN(BMesh *bm, const char itype, void *data, int *r_len,