py/obj: Add static safety checks to mp_obj_is_type().
Commit d96cfd13e3a464862c introduced a regression by breaking existing
users of mp_obj_is_type(.., &mp_obj_bool). This function (and associated
helpers like mp_obj_is_int()) have some specific nuances, and mistakes like
this one can happen again.
This commit adds mp_obj_is_exact_type() which behaves like the the old
mp_obj_is_type(). The new mp_obj_is_type() has the same prototype but it
attempts to statically assert that it's not called with types which should
be checked using mp_obj_is_type(). If called with any of these types: int,
str, bool, NoneType - it will cause a compilation error. Additional
checked types (e.g function types) can be added in the future.
Existing users of mp_obj_is_type() with the now "invalid" types, were
translated to use mp_obj_is_exact_type().
The use of MP_STATIC_ASSERT() is not bulletproof - usually GCC (and other
compilers) can't statically check conditions that are only known during
link-time (like variables' addresses comparison). However, in this case,
GCC is able to statically detect these conditions, probably because it's
the exact same object - `&mp_type_int == &mp_type_int` is detected.
Misuses of this function with runtime-chosen types (e.g:
`mp_obj_type_t *x = ...; mp_obj_is_type(..., x);` won't be detected. MSC
is unable to detect this, so we use MP_STATIC_ASSERT_NOT_MSC().
Compiling with this commit and without the fix for d96cfd13e3a464862c shows
that it detects the problem.
Signed-off-by: Yonatan Goldschmidt <yon.goldschmidt@gmail.com>
diff --git a/py/objint.c b/py/objint.c
index 5ff5e7d..740e7ea 100644
--- a/py/objint.c
+++ b/py/objint.c
@@ -232,7 +232,7 @@
// A small int; get the integer value to format.
num = MP_OBJ_SMALL_INT_VALUE(self_in);
} else {
- assert(mp_obj_is_type(self_in, &mp_type_int));
+ assert(mp_obj_is_exact_type(self_in, &mp_type_int));
// Not a small int.
#if MICROPY_LONGINT_IMPL == MICROPY_LONGINT_IMPL_LONGLONG
const mp_obj_int_t *self = self_in;