fix [#35150] Crash when bmesh operation called from within a Panel draw()

accessing a bmesh from python would reallocate all customdata layers.

add an assert to BM_data_layer_free(), when its called unnecessarily since its reallocating all layers.

2 files changed, 15 insertions, 6 deletions

diff --git a/source/blender/bmesh/intern/bmesh_interp.c b/source/blender/bmesh/intern/bmesh_interp.c
index c0975897090..290c6d9c9c8 100644
--- a/source/blender/bmesh/intern/bmesh_interp.c
+++ b/source/blender/bmesh/intern/bmesh_interp.c
@@ -804,6 +804,7 @@ void BM_data_layer_add_named(BMesh *bm, CustomData *data, int type, const char *
 void BM_data_layer_free(BMesh *bm, CustomData *data, int type)
 {
 	CustomData olddata;
+	bool has_layer;
 
 	olddata = *data;
 	olddata.layers = (olddata.layers) ? MEM_dupallocN(olddata.layers): NULL;
@@ -811,7 +812,9 @@ void BM_data_layer_free(BMesh *bm, CustomData *data, int type)
 	/* the pool is now owned by olddata and must not be shared */
 	data->pool = NULL;
 
-	CustomData_free_layer_active(data, type, 0);
+	has_layer = CustomData_free_layer_active(data, type, 0);
+	/* assert because its expensive to realloc - better not do if layer isnt present */
+	BLI_assert(has_layer != false);
 
 	update_data_blocks(bm, &olddata, data);
 	if (olddata.layers) MEM_freeN(olddata.layers);
@@ -820,6 +823,7 @@ void BM_data_layer_free(BMesh *bm, CustomData *data, int type)
 void BM_data_layer_free_n(BMesh *bm, CustomData *data, int type, int n)
 {
 	CustomData olddata;
+	bool has_layer;
 
 	olddata = *data;
 	olddata.layers = (olddata.layers) ? MEM_dupallocN(olddata.layers): NULL;
@@ -827,7 +831,9 @@ void BM_data_layer_free_n(BMesh *bm, CustomData *data, int type, int n)
 	/* the pool is now owned by olddata and must not be shared */
 	data->pool = NULL;
 
-	CustomData_free_layer(data, type, 0, CustomData_get_layer_index_n(data, type, n));
+	has_layer = CustomData_free_layer(data, type, 0, CustomData_get_layer_index_n(data, type, n));
+	/* assert because its expensive to realloc - better not do if layer isnt present */
+	BLI_assert(has_layer != false);
 	
 	update_data_blocks(bm, &olddata, data);
 	if (olddata.layers) MEM_freeN(olddata.layers);
diff --git a/source/blender/python/bmesh/bmesh_py_types.c b/source/blender/python/bmesh/bmesh_py_types.c
index fc69f81820a..3da47d22d90 100644
--- a/source/blender/python/bmesh/bmesh_py_types.c
+++ b/source/blender/python/bmesh/bmesh_py_types.c
@@ -2943,10 +2943,10 @@ static void bpy_bmesh_dealloc(BPy_BMesh *self)
 	if (bm) {
 		bm_dealloc_editmode_warn(self);
 
-		BM_data_layer_free(bm, &bm->vdata, CD_BM_ELEM_PYPTR);
-		BM_data_layer_free(bm, &bm->edata, CD_BM_ELEM_PYPTR);
-		BM_data_layer_free(bm, &bm->pdata, CD_BM_ELEM_PYPTR);
-		BM_data_layer_free(bm, &bm->ldata, CD_BM_ELEM_PYPTR);
+		if (CustomData_has_layer(&bm->vdata, CD_BM_ELEM_PYPTR)) BM_data_layer_free(bm, &bm->vdata, CD_BM_ELEM_PYPTR);
+		if (CustomData_has_layer(&bm->edata, CD_BM_ELEM_PYPTR)) BM_data_layer_free(bm, &bm->edata, CD_BM_ELEM_PYPTR);
+		if (CustomData_has_layer(&bm->pdata, CD_BM_ELEM_PYPTR)) BM_data_layer_free(bm, &bm->pdata, CD_BM_ELEM_PYPTR);
+		if (CustomData_has_layer(&bm->ldata, CD_BM_ELEM_PYPTR)) BM_data_layer_free(bm, &bm->ldata, CD_BM_ELEM_PYPTR);
 
 		bm->py_handle = NULL;
 
@@ -3370,10 +3370,13 @@ PyObject *BPy_BMesh_CreatePyObject(BMesh *bm, int flag)
 
 		bm->py_handle = self; /* point back */
 
+		/* avoid allocating layers when we don't have to */
+#if 0
 		BM_data_layer_add(bm, &bm->vdata, CD_BM_ELEM_PYPTR);
 		BM_data_layer_add(bm, &bm->edata, CD_BM_ELEM_PYPTR);
 		BM_data_layer_add(bm, &bm->pdata, CD_BM_ELEM_PYPTR);
 		BM_data_layer_add(bm, &bm->ldata, CD_BM_ELEM_PYPTR);
+#endif
 	}
 
 	return (PyObject *)self;