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py/objtype: Refactor object's handling of __new__ to not create 2 objs.

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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.
This commit is contained in:
Damien George 2017-12-12 15:22:03 +11:00
parent 3c28df1658
commit c78ef92d78
3 changed files with 37 additions and 34 deletions
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9
py/objobject.c
View File

@ -52,9 +52,12 @@ STATIC mp_obj_t object___new__(mp_obj_t cls) {
if (!MP_OBJ_IS_TYPE(cls, &mp_type_type) || !mp_obj_is_instance_type((mp_obj_type_t*)MP_OBJ_TO_PTR(cls))) {
mp_raise_TypeError("__new__ arg must be a user-type");
}
mp_obj_t o = MP_OBJ_SENTINEL;
mp_obj_t res = mp_obj_instance_make_new(MP_OBJ_TO_PTR(cls), 1, 0, &o);
return res;
// This executes only "__new__" part of instance creation.
// TODO: This won't work well for classes with native bases.
// TODO: This is a hack, should be resolved along the lines of
// https://github.com/micropython/micropython/issues/606#issuecomment-43685883
const mp_obj_type_t *native_base;
return MP_OBJ_FROM_PTR(mp_obj_new_instance(MP_OBJ_TO_PTR(cls), &native_base));
}
STATIC MP_DEFINE_CONST_FUN_OBJ_1(object___new___fun_obj, object___new__);
STATIC MP_DEFINE_CONST_STATICMETHOD_OBJ(object___new___obj, MP_ROM_PTR(&object___new___fun_obj));

57
py/objtype.c
View File

@ -90,17 +90,22 @@ STATIC mp_obj_t native_base_init_wrapper(size_t n_args, const mp_obj_t *args) {
}
STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(native_base_init_wrapper_obj, 1, MP_OBJ_FUN_ARGS_MAX, native_base_init_wrapper);
STATIC mp_obj_t mp_obj_new_instance(const mp_obj_type_t *class, size_t subobjs) {
mp_obj_instance_t *o = m_new_obj_var(mp_obj_instance_t, mp_obj_t, subobjs);
#if !MICROPY_CPYTHON_COMPAT
STATIC
#endif
mp_obj_instance_t *mp_obj_new_instance(const mp_obj_type_t *class, const mp_obj_type_t **native_base) {
size_t num_native_bases = instance_count_native_bases(class, native_base);
assert(num_native_bases < 2);
mp_obj_instance_t *o = m_new_obj_var(mp_obj_instance_t, mp_obj_t, num_native_bases);
o->base.type = class;
mp_map_init(&o->members, 0);
// Initialise the native base-class slot (should be 1 at most) with a valid
// object. It doesn't matter which object, so long as it can be uniquely
// distinguished from a native class that is initialised.
if (subobjs != 0) {
if (num_native_bases != 0) {
o->subobj[0] = MP_OBJ_FROM_PTR(&native_base_init_wrapper_obj);
}
return MP_OBJ_FROM_PTR(o);
return o;
}
// TODO
@ -267,20 +272,6 @@ STATIC void instance_print(const mp_print_t *print, mp_obj_t self_in, mp_print_k
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) {
assert(mp_obj_is_instance_type(self));
const mp_obj_type_t *native_base = NULL;
size_t num_native_bases = instance_count_native_bases(self, &native_base);
assert(num_native_bases < 2);
mp_obj_instance_t *o = MP_OBJ_TO_PTR(mp_obj_new_instance(self, num_native_bases));
// This executes only "__new__" part of instance creation.
// TODO: This won't work well for classes with native bases.
// TODO: This is a hack, should be resolved along the lines of
// https://github.com/micropython/micropython/issues/606#issuecomment-43685883
if (n_args == 1 && *args == MP_OBJ_SENTINEL) {
return MP_OBJ_FROM_PTR(o);
}
// look for __new__ function
mp_obj_t init_fn[2] = {MP_OBJ_NULL};
struct class_lookup_data lookup = {
@ -292,10 +283,12 @@ mp_obj_t mp_obj_instance_make_new(const mp_obj_type_t *self, size_t n_args, size
};
mp_obj_class_lookup(&lookup, self);
mp_obj_t new_ret = MP_OBJ_FROM_PTR(o);
if (init_fn[0] == MP_OBJ_SENTINEL) {
// Native type's constructor is what wins - it gets all our arguments,
// and none Python classes are initialized at all.
const mp_obj_type_t *native_base = NULL;
mp_obj_instance_t *o;
if (init_fn[0] == MP_OBJ_NULL || init_fn[0] == MP_OBJ_SENTINEL) {
// Either there is no __new__() method defined or there is a native
// constructor. In both cases create a blank instance.
o = mp_obj_new_instance(self, &native_base);
// Since type->make_new() implements both __new__() and __init__() in
// one go, of which the latter may be overridden by the Python subclass,
@ -303,8 +296,9 @@ mp_obj_t mp_obj_instance_make_new(const mp_obj_type_t *self, size_t n_args, size
// constructor to give a chance for the Python __init__() method to call
// said native constructor.
} else if (init_fn[0] != MP_OBJ_NULL) {
// now call Python class __new__ function with all args
} else {
// Call Python class __new__ function with all args to create an instance
mp_obj_t new_ret;
if (n_args == 0 && n_kw == 0) {
mp_obj_t args2[1] = {MP_OBJ_FROM_PTR(self)};
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
m_del(mp_obj_t, args2, 1 + n_args + 2 * n_kw);
}
}
// https://docs.python.org/3.4/reference/datamodel.html#object.__new__
// "If __new__() does not return an instance of cls, then the new
// instance's __init__() method will not be invoked."
if (mp_obj_get_type(new_ret) != self) {
return new_ret;
}
// https://docs.python.org/3.4/reference/datamodel.html#object.__new__
// "If __new__() does not return an instance of cls, then the new instance's __init__() method will not be invoked."
if (mp_obj_get_type(new_ret) != self) {
return new_ret;
// The instance returned by __new__() becomes the new object
o = MP_OBJ_TO_PTR(new_ret);
}
o = MP_OBJ_TO_PTR(new_ret);
// now call Python class __init__ function with all args
// This method has a chance to call super().__init__() to construct a
// possible native base class.

5
py/objtype.h
View File

@ -37,6 +37,11 @@ typedef struct _mp_obj_instance_t {
// TODO maybe cache __getattr__ and __setattr__ for efficient lookup of them
} mp_obj_instance_t;
#if MICROPY_CPYTHON_COMPAT
// this is needed for object.__new__
mp_obj_instance_t *mp_obj_new_instance(const mp_obj_type_t *cls, const mp_obj_type_t **native_base);
#endif
// this needs to be exposed for MICROPY_OPT_CACHE_MAP_LOOKUP_IN_BYTECODE to work
void mp_obj_instance_attr(mp_obj_t self_in, qstr attr, mp_obj_t *dest);