Add SystemExit exception and use it in unix/ and stmhal/ ports.

Addresses issue #598.

py/obj.h

@@ -344,6 +344,7 @@ extern const mp_obj_type_t mp_type_RuntimeError;
 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_SystemError;
+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_ValueError;
 extern const mp_obj_type_t mp_type_ZeroDivisionError;

py/objexcept.c

@@ -159,7 +159,7 @@ const mp_obj_type_t mp_type_ ## exc_name = { \
 // List of all exceptions, arranged as in the table at:
 // http://docs.python.org/3.3/library/exceptions.html
 MP_DEFINE_EXCEPTION_BASE(BaseException)
-//MP_DEFINE_EXCEPTION(SystemExit, BaseException)
+MP_DEFINE_EXCEPTION(SystemExit, BaseException)
 //MP_DEFINE_EXCEPTION(KeyboardInterrupt, BaseException)
 MP_DEFINE_EXCEPTION(GeneratorExit, BaseException)
 MP_DEFINE_EXCEPTION(Exception, BaseException)

py/qstrdefs.h

@@ -102,6 +102,7 @@ Q(OverflowError)
 Q(RuntimeError)
 Q(SyntaxError)
 Q(SystemError)
+Q(SystemExit)
 Q(TypeError)
 Q(UnboundLocalError)
 Q(ValueError)

stmhal/main.c

@@ -556,7 +556,6 @@ STATIC NORETURN mp_obj_t mp_sys_exit(uint n_args, const mp_obj_t *args) {
     if (n_args > 0) {
         rc = mp_obj_get_int(args[0]);
     }
-    nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_NotImplementedError,
-        "sys.exit(%d) called, is not fully implemented", rc));
+    nlr_raise(mp_obj_new_exception_arg1(&mp_type_SystemExit, mp_obj_new_int(rc)));
 }
 MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mp_sys_exit_obj, 0, 1, mp_sys_exit);

unix/main.c

@@ -123,6 +123,11 @@ STATIC int execute_from_lexer(mp_lexer_t *lex, mp_parse_input_kind_t input_kind,
         return 0;
     } else {
         // uncaught exception
+        // check for SystemExit
+        mp_obj_t exc = (mp_obj_t)nlr.ret_val;
+        if (mp_obj_is_subclass_fast(mp_obj_get_type(exc), &mp_type_SystemExit)) {
+            exit(mp_obj_get_int(mp_obj_exception_get_value(exc)));
+        }
         mp_obj_print_exception((mp_obj_t)nlr.ret_val);
         return 1;
     }
@@ -383,7 +388,7 @@ STATIC mp_obj_t mp_sys_exit(uint n_args, const mp_obj_t *args) {
     if (n_args > 0) {
         rc = mp_obj_get_int(args[0]);
     }
-    exit(rc);
+    nlr_raise(mp_obj_new_exception_arg1(&mp_type_SystemExit, mp_obj_new_int(rc)));
 }
 MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mp_sys_exit_obj, 0, 1, mp_sys_exit);