Check native object in case of early access

If a native displayio object is accessed before it's super().__init__()
has been called, then a placeholder is given that will cause a crash if
accessed. This is tricky to get right so we detect this case and raise
a NotInplementedError instead of crashing.

Fixes adafruit#1881

Author: tannewt

py/objtype.c

@@ -117,6 +117,16 @@ mp_obj_instance_t *mp_obj_new_instance(const mp_obj_type_t *class, const mp_obj_
     return o;
 }
 
+// When instances are first created they have the base_init wrapper as their native parent's
+// instance because make_new combines __new__ and __init__. This object is invalid for the native
+// code so it must call this method to ensure that the given object has been __init__'d and is
+// valid.
+void mp_obj_assert_native_inited(mp_obj_t native_object) {
+    if (native_object == MP_OBJ_FROM_PTR(&native_base_init_wrapper_obj)) {
+        mp_raise_NotImplementedError(translate("Call super().__init__() before accessing native object."));
+    }
+}
+
 // TODO
 // This implements depth-first left-to-right MRO, which is not compliant with Python3 MRO
 // http://python-history.blogspot.com/2010/06/method-resolution-order.html

py/objtype.h

@@ -37,6 +37,8 @@ typedef struct _mp_obj_instance_t {
     // TODO maybe cache __getattr__ and __setattr__ for efficient lookup of them
 } mp_obj_instance_t;
 
+void mp_obj_assert_native_inited(mp_obj_t native_object);
+
 #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);

shared-bindings/_stage/__init__.c

@@ -85,6 +85,7 @@ STATIC mp_obj_t stage_render(size_t n_args, const mp_obj_t *args) {
 
     mp_obj_t native_display = mp_instance_cast_to_native_base(args[6],
         &displayio_display_type);
+    mp_obj_assert_native_inited(native_display);
     if (!MP_OBJ_IS_TYPE(native_display, &displayio_display_type)) {
         mp_raise_TypeError(translate("argument num/types mismatch"));
     }

shared-bindings/displayio/Display.c

@@ -31,6 +31,7 @@
 #include "lib/utils/context_manager_helpers.h"
 #include "py/binary.h"
 #include "py/objproperty.h"
+#include "py/objtype.h"
 #include "py/runtime.h"
 #include "shared-bindings/displayio/Group.h"
 #include "shared-bindings/microcontroller/Pin.h"
@@ -172,6 +173,7 @@ STATIC mp_obj_t displayio_display_make_new(const mp_obj_type_t *type, size_t n_a
 // Helper to ensure we have the native super class instead of a subclass.
 static displayio_display_obj_t* native_display(mp_obj_t display_obj) {
     mp_obj_t native_display = mp_instance_cast_to_native_base(display_obj, &displayio_display_type);
+    mp_obj_assert_native_inited(native_display);
     return MP_OBJ_TO_PTR(native_display);
 }
 
@@ -184,11 +186,7 @@ STATIC mp_obj_t displayio_display_obj_show(mp_obj_t self_in, mp_obj_t group_in)
     displayio_display_obj_t *self = native_display(self_in);
     displayio_group_t* group = NULL;
     if (group_in != mp_const_none) {
-        mp_obj_t native_layer = mp_instance_cast_to_native_base(group_in, &displayio_group_type);
-        if (native_layer == MP_OBJ_NULL) {
-            mp_raise_ValueError(translate("Must be a Group subclass."));
-        }
-        group = MP_OBJ_TO_PTR(native_layer);
+        group = MP_OBJ_TO_PTR(native_group(group_in));
     }
 
     common_hal_displayio_display_show(self, group);

shared-bindings/displayio/Group.c

@@ -31,6 +31,7 @@
 #include "lib/utils/context_manager_helpers.h"
 #include "py/binary.h"
 #include "py/objproperty.h"
+#include "py/objtype.h"
 #include "py/runtime.h"
 #include "supervisor/shared/translate.h"
 
@@ -80,8 +81,12 @@ STATIC mp_obj_t displayio_group_make_new(const mp_obj_type_t *type, size_t n_arg
 }
 
 // Helper to ensure we have the native super class instead of a subclass.
-static displayio_group_t* native_group(mp_obj_t group_obj) {
+displayio_group_t* native_group(mp_obj_t group_obj) {
     mp_obj_t native_group = mp_instance_cast_to_native_base(group_obj, &displayio_group_type);
+    if (native_group == MP_OBJ_NULL) {
+        mp_raise_ValueError_varg(translate("Must be a %q subclass."), MP_QSTR_Group);
+    }
+    mp_obj_assert_native_inited(native_group);
     return MP_OBJ_TO_PTR(native_group);
 }
 

shared-bindings/displayio/Group.h

@@ -31,6 +31,7 @@
 
 extern const mp_obj_type_t displayio_group_type;
 
+displayio_group_t* native_group(mp_obj_t group_obj);
 
 void common_hal_displayio_group_construct(displayio_group_t* self, uint32_t max_size, uint32_t scale, mp_int_t x, mp_int_t y);
 uint32_t common_hal_displayio_group_get_scale(displayio_group_t* self);

shared-bindings/displayio/TileGrid.c

@@ -31,6 +31,7 @@
 #include "lib/utils/context_manager_helpers.h"
 #include "py/binary.h"
 #include "py/objproperty.h"
+#include "py/objtype.h"
 #include "py/runtime.h"
 #include "shared-bindings/displayio/Bitmap.h"
 #include "shared-bindings/displayio/ColorConverter.h"
@@ -139,6 +140,7 @@ STATIC mp_obj_t displayio_tilegrid_make_new(const mp_obj_type_t *type, size_t n_
 // Helper to ensure we have the native super class instead of a subclass.
 static displayio_tilegrid_t* native_tilegrid(mp_obj_t tilegrid_obj) {
     mp_obj_t native_tilegrid = mp_instance_cast_to_native_base(tilegrid_obj, &displayio_tilegrid_type);
+    mp_obj_assert_native_inited(native_tilegrid);
     return MP_OBJ_TO_PTR(native_tilegrid);
 }
 

shared-bindings/socket/__init__.c

@@ -257,7 +257,7 @@ STATIC mp_int_t _socket_recv_into(mod_network_socket_obj_t *sock, byte *buf, mp_
 //|   Reads some bytes from the connected remote address, writing
 //|   into the provided buffer. If bufsize <= len(buffer) is given,
 //|   a maximum of bufsize bytes will be read into the buffer. If no
-//|   valid value is given for bufsize, the default is the length of 
+//|   valid value is given for bufsize, the default is the length of
 //|   the given buffer.
 //|
 //|   Suits sockets of type SOCK_STREAM
@@ -274,13 +274,14 @@ STATIC mp_obj_t socket_recv_into(size_t n_args, const mp_obj_t *args) {
     }
     mp_buffer_info_t bufinfo;
     mp_get_buffer_raise(args[1], &bufinfo, MP_BUFFER_WRITE);
-    mp_int_t len;
+    mp_int_t len = bufinfo.len;
     if (n_args == 3) {
-        len = mp_obj_get_int(args[2]);
-    }
-    if (n_args == 2 || (size_t) len > bufinfo.len) {
-        len = bufinfo.len;
+        mp_int_t given_len = mp_obj_get_int(args[2]);
+        if (given_len < len) {
+            len = given_len;
+        }
     }
+
     mp_int_t ret = _socket_recv_into(self, (byte*)bufinfo.buf, len);
     return mp_obj_new_int_from_uint(ret);
 }