DNA/RNA: add 'py_instance' for ID types

Avoid creating new Python instances
every time a scene, object, mesh .. etc are accessed.

Also resolves crashes T28724, T53530
although it's only valid for ID types, not modifiers vertices etc.

Back-ported from blender2.8 branch.

1 files changed, 32 insertions, 12 deletions

diff --git a/source/blender/python/intern/bpy_rna.c b/source/blender/python/intern/bpy_rna.c
index 1a9fd920af5..deb045c514b 100644
--- a/source/blender/python/intern/bpy_rna.c
+++ b/source/blender/python/intern/bpy_rna.c
@@ -6762,7 +6762,30 @@ PyObject *pyrna_struct_CreatePyObject(PointerRNA *ptr)
 	if (ptr->data == NULL && ptr->type == NULL) { /* Operator RNA has NULL data */
 		Py_RETURN_NONE;
 	}
-	else {
+
+	/* New in 2.8x, since not many types support instancing
+	 * we may want to use a flag to avoid looping over all classes. - campbell */
+	void **instance = ptr->data ? RNA_struct_instance(ptr) : NULL;
+	if (instance && *instance) {
+		pyrna = *instance;
+
+		/* Refine may have changed types after the first instance was created. */
+		if (ptr->type == pyrna->ptr.type) {
+			Py_INCREF(pyrna);
+			return (PyObject *)pyrna;
+		}
+		else {
+			/* Existing users will need to use 'type_recast' method. */
+			Py_DECREF(pyrna);
+			*instance = NULL;
+			/* Continue as if no instance was made */
+#if 0		/* no need to assign, will be written to next... */
+			pyrna = NULL;
+#endif
+		}
+	}
+
+	{
 		PyTypeObject *tp = (PyTypeObject *)pyrna_struct_Subtype(ptr);
 
 		if (tp) {
@@ -6783,6 +6806,12 @@ PyObject *pyrna_struct_CreatePyObject(PointerRNA *ptr)
 		return NULL;
 	}
 
+	/* Blender's instance owns a reference (to avoid Python freeing it). */
+	if (instance) {
+		*instance = pyrna;
+		Py_INCREF(pyrna);
+	}
+
 	pyrna->ptr = *ptr;
 #ifdef PYRNA_FREE_SUPPORT
 	pyrna->freeptr = false;
@@ -7547,7 +7576,6 @@ static int bpy_class_call(bContext *C, PointerRNA *ptr, FunctionRNA *func, Param
 	PyObject *args;
 	PyObject *ret = NULL, *py_srna = NULL, *py_class_instance = NULL, *parmitem;
 	PyTypeObject *py_class;
-	void **py_class_instance_store = NULL;
 	PropertyRNA *parm;
 	ParameterIterator iter;
 	PointerRNA funcptr;
@@ -7562,7 +7590,7 @@ static int bpy_class_call(bContext *C, PointerRNA *ptr, FunctionRNA *func, Param
 	PyGILState_STATE gilstate;
 
 #ifdef USE_PEDANTIC_WRITE
-	const bool is_operator = RNA_struct_is_a(ptr->type, &RNA_Operator);
+	const bool is_readonly_init = !RNA_struct_is_a(ptr->type, &RNA_Operator);
 	// const char *func_id = RNA_function_identifier(func);  /* UNUSED */
 	/* testing, for correctness, not operator and not draw function */
 	const bool is_readonly = !(RNA_function_flag(func) & FUNC_ALLOW_WRITE);
@@ -7597,10 +7625,6 @@ static int bpy_class_call(bContext *C, PointerRNA *ptr, FunctionRNA *func, Param
 					py_class_instance = *instance;
 					Py_INCREF(py_class_instance);
 				}
-				else {
-					/* store the instance here once its created */
-					py_class_instance_store = instance;
-				}
 			}
 		}
 		/* end exception */
@@ -7627,7 +7651,7 @@ static int bpy_class_call(bContext *C, PointerRNA *ptr, FunctionRNA *func, Param
 			if (py_class->tp_init) {
 #ifdef USE_PEDANTIC_WRITE
 				const int prev_write = rna_disallow_writes;
-				rna_disallow_writes = is_operator ? false : true;  /* only operators can write on __init__ */
+				rna_disallow_writes = is_readonly_init ? false : true;  /* only operators can write on __init__ */
 #endif
 
 				/* true in most cases even when the class its self doesn't define an __init__ function. */
@@ -7671,10 +7695,6 @@ static int bpy_class_call(bContext *C, PointerRNA *ptr, FunctionRNA *func, Param
 			if (py_class_instance == NULL) {
 				err = -1; /* so the error is not overridden below */
 			}
-			else if (py_class_instance_store) {
-				*py_class_instance_store = py_class_instance;
-				Py_INCREF(py_class_instance);
-			}
 		}
 	}