py: Introduce MP_ROM_NONE macro for ROM to refer to None object.

This helps to prevent mistakes, and allows easily changing the ROM value of
None if needed.

1 files changed, 4 insertions, 0 deletions

diff --git a/py/obj.h b/py/obj.h
index 7c6815a3c..189f37d07 100644
--- a/py/obj.h
+++ b/py/obj.h
@@ -242,6 +242,10 @@ typedef union _mp_rom_obj_t { uint64_t u64; struct { const void *lo, *hi; } u32;
 
 // Macros to create objects that are stored in ROM.
 
+#ifndef MP_ROM_NONE
+#define MP_ROM_NONE MP_ROM_PTR(&mp_const_none_obj)
+#endif
+
 #ifndef MP_ROM_INT
 typedef mp_const_obj_t mp_rom_obj_t;
 #define MP_ROM_INT(i) MP_OBJ_NEW_SMALL_INT(i)