py/objexcept: Add uncatchable SystemAbort exception.

laurensvalk · laurensvalk · commit 07802c22b99a · 2022-11-14T14:00:56.000+01:00
This adds an exception type that forces MicroPython to exit even if the
user MicroPython script catches all exceptions.

This exception can be raised by C code to force MicroPython to exit for
safety reasons, such as very low battery or very high temperatures.

Signed-off-by: Laurens Valk &lt;laurens@pybricks.com&gt;
diff --git a/py/obj.h b/py/obj.h
@@ -854,6 +854,7 @@ extern const mp_obj_type_t mp_type_RuntimeError;
 extern const mp_obj_type_t mp_type_StopAsyncIteration;
 extern const mp_obj_type_t mp_type_StopIteration;
 extern const mp_obj_type_t mp_type_SyntaxError;
+extern const mp_obj_type_t mp_type_SystemAbort;
 extern const mp_obj_type_t mp_type_SystemExit;
 extern const mp_obj_type_t mp_type_TypeError;
 extern const mp_obj_type_t mp_type_UnicodeError;
diff --git a/py/objexcept.c b/py/objexcept.c
@@ -376,6 +376,10 @@ MP_DEFINE_EXCEPTION(Exception, BaseException)
     MP_DEFINE_EXCEPTION(ResourceWarning, Warning)
     */
 
+// Exception that can't be raised or caught by user code, not even with a
+// bare except. Can be used to force MicroPython to exit from C code.
+MP_DEFINE_EXCEPTION(SystemAbort, BaseException)
+
 // *FORMAT-ON*
 
 mp_obj_t mp_obj_new_exception(const mp_obj_type_t *exc_type) {
diff --git a/py/vm.c b/py/vm.c
@@ -1441,8 +1441,8 @@ unwind_jump:;
                 POP_EXC_BLOCK();
             }
 
-            if (exc_sp >= exc_stack) {
-                // catch exception and pass to byte code
+            if (exc_sp >= exc_stack && !mp_obj_is_type(MP_OBJ_FROM_PTR(nlr.ret_val), &mp_type_SystemAbort)) {
+                // catch exception (but not SystemAbort) and pass to byte code
                 code_state->ip = exc_sp->handler;
                 mp_obj_t *sp = MP_TAGPTR_PTR(exc_sp->val_sp);
                 // save this exception in the stack so it can be used in a reraise, if needed
