Skip to content

Commit c78ef92

Browse files
dpgeorgedpgeorge
committed
py/objtype: Refactor object's handling of __new__ to not create 2 objs.
Before this patch, if a user defined the __new__() function for a class then two instances of that class would be created: once before __new__ is called and once during the __new__ call (assuming the user creates some instance, eg using super().__new__, which is most of the time). The first one was then discarded. This refactor makes it so that a new instance is only created if the user __new__ function doesn't exist.
1 parent 3c28df1 commit c78ef92

3 files changed

Lines changed: 37 additions & 34 deletions

File tree

‎py/objobject.c‎

Lines changed: 6 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -52,9 +52,12 @@ STATIC mp_obj_t object___new__(mp_obj_t cls) {
5252
if (!MP_OBJ_IS_TYPE(cls, &mp_type_type) || !mp_obj_is_instance_type((mp_obj_type_t*)MP_OBJ_TO_PTR(cls))) {
5353
mp_raise_TypeError("__new__ arg must be a user-type");
5454
}
55-
mp_obj_t o = MP_OBJ_SENTINEL;
56-
mp_obj_t res = mp_obj_instance_make_new(MP_OBJ_TO_PTR(cls), 1, 0, &o);
57-
return res;
55+
// This executes only "__new__" part of instance creation.
56+
// TODO: This won't work well for classes with native bases.
57+
// TODO: This is a hack, should be resolved along the lines of
58+
// https://github.com/micropython/micropython/issues/606#issuecomment-43685883
59+
const mp_obj_type_t *native_base;
60+
return MP_OBJ_FROM_PTR(mp_obj_new_instance(MP_OBJ_TO_PTR(cls), &native_base));
5861
}
5962
STATIC MP_DEFINE_CONST_FUN_OBJ_1(object___new___fun_obj, object___new__);
6063
STATIC MP_DEFINE_CONST_STATICMETHOD_OBJ(object___new___obj, MP_ROM_PTR(&object___new___fun_obj));

‎py/objtype.c‎

Lines changed: 26 additions & 31 deletions
Original file line numberDiff line numberDiff line change
@@ -90,17 +90,22 @@ STATIC mp_obj_t native_base_init_wrapper(size_t n_args, const mp_obj_t *args) {
9090
}
9191
STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(native_base_init_wrapper_obj, 1, MP_OBJ_FUN_ARGS_MAX, native_base_init_wrapper);
9292

93-
STATIC mp_obj_t mp_obj_new_instance(const mp_obj_type_t *class, size_t subobjs) {
94-
mp_obj_instance_t *o = m_new_obj_var(mp_obj_instance_t, mp_obj_t, subobjs);
93+
#if !MICROPY_CPYTHON_COMPAT
94+
STATIC
95+
#endif
96+
mp_obj_instance_t *mp_obj_new_instance(const mp_obj_type_t *class, const mp_obj_type_t **native_base) {
97+
size_t num_native_bases = instance_count_native_bases(class, native_base);
98+
assert(num_native_bases < 2);
99+
mp_obj_instance_t *o = m_new_obj_var(mp_obj_instance_t, mp_obj_t, num_native_bases);
95100
o->base.type = class;
96101
mp_map_init(&o->members, 0);
97102
// Initialise the native base-class slot (should be 1 at most) with a valid
98103
// object. It doesn't matter which object, so long as it can be uniquely
99104
// distinguished from a native class that is initialised.
100-
if (subobjs != 0) {
105+
if (num_native_bases != 0) {
101106
o->subobj[0] = MP_OBJ_FROM_PTR(&native_base_init_wrapper_obj);
102107
}
103-
return MP_OBJ_FROM_PTR(o);
108+
return o;
104109
}
105110

106111
// TODO
@@ -267,20 +272,6 @@ STATIC void instance_print(const mp_print_t *print, mp_obj_t self_in, mp_print_k
267272
mp_obj_t mp_obj_instance_make_new(const mp_obj_type_t *self, size_t n_args, size_t n_kw, const mp_obj_t *args) {
268273
assert(mp_obj_is_instance_type(self));
269274

270-
const mp_obj_type_t *native_base = NULL;
271-
size_t num_native_bases = instance_count_native_bases(self, &native_base);
272-
assert(num_native_bases < 2);
273-
274-
mp_obj_instance_t *o = MP_OBJ_TO_PTR(mp_obj_new_instance(self, num_native_bases));
275-
276-
// This executes only "__new__" part of instance creation.
277-
// TODO: This won't work well for classes with native bases.
278-
// TODO: This is a hack, should be resolved along the lines of
279-
// https://github.com/micropython/micropython/issues/606#issuecomment-43685883
280-
if (n_args == 1 && *args == MP_OBJ_SENTINEL) {
281-
return MP_OBJ_FROM_PTR(o);
282-
}
283-
284275
// look for __new__ function
285276
mp_obj_t init_fn[2] = {MP_OBJ_NULL};
286277
struct class_lookup_data lookup = {
@@ -292,19 +283,22 @@ mp_obj_t mp_obj_instance_make_new(const mp_obj_type_t *self, size_t n_args, size
292283
};
293284
mp_obj_class_lookup(&lookup, self);
294285

295-
mp_obj_t new_ret = MP_OBJ_FROM_PTR(o);
296-
if (init_fn[0] == MP_OBJ_SENTINEL) {
297-
// Native type's constructor is what wins - it gets all our arguments,
298-
// and none Python classes are initialized at all.
286+
const mp_obj_type_t *native_base = NULL;
287+
mp_obj_instance_t *o;
288+
if (init_fn[0] == MP_OBJ_NULL || init_fn[0] == MP_OBJ_SENTINEL) {
289+
// Either there is no __new__() method defined or there is a native
290+
// constructor. In both cases create a blank instance.
291+
o = mp_obj_new_instance(self, &native_base);
299292

300293
// Since type->make_new() implements both __new__() and __init__() in
301294
// one go, of which the latter may be overridden by the Python subclass,
302295
// we defer (see the end of this function) the call of the native
303296
// constructor to give a chance for the Python __init__() method to call
304297
// said native constructor.
305298

306-
} else if (init_fn[0] != MP_OBJ_NULL) {
307-
// now call Python class __new__ function with all args
299+
} else {
300+
// Call Python class __new__ function with all args to create an instance
301+
mp_obj_t new_ret;
308302
if (n_args == 0 && n_kw == 0) {
309303
mp_obj_t args2[1] = {MP_OBJ_FROM_PTR(self)};
310304
new_ret = mp_call_function_n_kw(init_fn[0], 1, 0, args2);
@@ -316,16 +310,17 @@ mp_obj_t mp_obj_instance_make_new(const mp_obj_type_t *self, size_t n_args, size
316310
m_del(mp_obj_t, args2, 1 + n_args + 2 * n_kw);
317311
}
318312

319-
}
313+
// https://docs.python.org/3.4/reference/datamodel.html#object.__new__
314+
// "If __new__() does not return an instance of cls, then the new
315+
// instance's __init__() method will not be invoked."
316+
if (mp_obj_get_type(new_ret) != self) {
317+
return new_ret;
318+
}
320319

321-
// https://docs.python.org/3.4/reference/datamodel.html#object.__new__
322-
// "If __new__() does not return an instance of cls, then the new instance's __init__() method will not be invoked."
323-
if (mp_obj_get_type(new_ret) != self) {
324-
return new_ret;
320+
// The instance returned by __new__() becomes the new object
321+
o = MP_OBJ_TO_PTR(new_ret);
325322
}
326323

327-
o = MP_OBJ_TO_PTR(new_ret);
328-
329324
// now call Python class __init__ function with all args
330325
// This method has a chance to call super().__init__() to construct a
331326
// possible native base class.

‎py/objtype.h‎

Lines changed: 5 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -37,6 +37,11 @@ typedef struct _mp_obj_instance_t {
3737
// TODO maybe cache __getattr__ and __setattr__ for efficient lookup of them
3838
} mp_obj_instance_t;
3939

40+
#if MICROPY_CPYTHON_COMPAT
41+
// this is needed for object.__new__
42+
mp_obj_instance_t *mp_obj_new_instance(const mp_obj_type_t *cls, const mp_obj_type_t **native_base);
43+
#endif
44+
4045
// this needs to be exposed for MICROPY_OPT_CACHE_MAP_LOOKUP_IN_BYTECODE to work
4146
void mp_obj_instance_attr(mp_obj_t self_in, qstr attr, mp_obj_t *dest);
4247

0 commit comments

Comments
 (0)