py: Use a wrapper to explicitly check self argument of builtin methods.

Previous to this patch a call such as list.append(1, 2) would lead to a
seg fault.  This is because list.append is a builtin method and the first
argument to such methods is always assumed to have the correct type.

Now, when a builtin method is extracted like this it is wrapped in a
checker object which checks the the type of the first argument before
calling the builtin function.

This feature is contrelled by MICROPY_BUILTIN_METHOD_CHECK_SELF_ARG and
is enabled by default.

See issue #1216.

1 files changed, 9 insertions, 0 deletions

diff --git a/py/mpconfig.h b/py/mpconfig.h
index 2d9288f32..9f541ef70 100644
--- a/py/mpconfig.h
+++ b/py/mpconfig.h
@@ -393,6 +393,15 @@ typedef double mp_float_t;
 #define MICROPY_CAN_OVERRIDE_BUILTINS (0)
 #endif
 
+// Whether to check that the "self" argument of a builtin method has the
+// correct type.  Such an explicit check is only needed if a builtin
+// method escapes to Python land without a first argument, eg
+// list.append([], 1).  Without this check such calls will have undefined
+// behaviour (usually segfault) if the first argument is the wrong type.
+#ifndef MICROPY_BUILTIN_METHOD_CHECK_SELF_ARG
+#define MICROPY_BUILTIN_METHOD_CHECK_SELF_ARG (1)
+#endif
+
 /*****************************************************************************/
 /* Fine control over Python builtins, classes, modules, etc                  */