traceback: fix for crash on non-native exceptions

Co-authored-by: Tim Hawes <[email protected]>

Author: microdev1

py/objexcept.c

@@ -104,7 +104,7 @@ mp_obj_t mp_alloc_emergency_exception_buf(mp_obj_t size_in) {
 #endif
 #endif  // MICROPY_ENABLE_EMERGENCY_EXCEPTION_BUF
 
-STATIC mp_obj_exception_t *get_native_exception(mp_obj_t self_in) {
+mp_obj_exception_t *mp_obj_exception_get_native(mp_obj_t self_in) {
     assert(mp_obj_is_exception_instance(self_in));
     if (mp_obj_is_native_exception_instance(self_in)) {
         return MP_OBJ_TO_PTR(self_in);
@@ -206,7 +206,7 @@ mp_obj_t mp_obj_exception_make_new(const mp_obj_type_t *type, size_t n_args, siz
 
 // Get exception "value" - that is, first argument, or None
 mp_obj_t mp_obj_exception_get_value(mp_obj_t self_in) {
-    mp_obj_exception_t *self = get_native_exception(self_in);
+    mp_obj_exception_t *self = mp_obj_exception_get_native(self_in);
     if (self->args->len == 0) {
         return mp_const_none;
     } else {
@@ -543,14 +543,14 @@ bool mp_obj_exception_match(mp_obj_t exc, mp_const_obj_t exc_type) {
 // traceback handling functions
 
 void mp_obj_exception_clear_traceback(mp_obj_t self_in) {
-    mp_obj_exception_t *self = get_native_exception(self_in);
+    mp_obj_exception_t *self = mp_obj_exception_get_native(self_in);
     // just set the traceback to the empty traceback object
     // we don't want to call any memory management functions here
     self->traceback = (mp_obj_traceback_t *)&mp_const_empty_traceback_obj;
 }
 
 void mp_obj_exception_add_traceback(mp_obj_t self_in, qstr file, size_t line, qstr block) {
-    mp_obj_exception_t *self = get_native_exception(self_in);
+    mp_obj_exception_t *self = mp_obj_exception_get_native(self_in);
 
     // Try to allocate memory for the traceback, with fallback to emergency traceback object
     if (self->traceback == NULL || self->traceback == (mp_obj_traceback_t *)&mp_const_empty_traceback_obj) {
@@ -612,7 +612,7 @@ void mp_obj_exception_add_traceback(mp_obj_t self_in, qstr file, size_t line, qs
 }
 
 void mp_obj_exception_get_traceback(mp_obj_t self_in, size_t *n, size_t **values) {
-    mp_obj_exception_t *self = get_native_exception(self_in);
+    mp_obj_exception_t *self = mp_obj_exception_get_native(self_in);
 
     if (self->traceback == NULL) {
         *n = 0;

py/objexcept.h

@@ -38,6 +38,7 @@ typedef struct _mp_obj_exception_t {
 
 void mp_obj_exception_print(const mp_print_t *print, mp_obj_t o_in, mp_print_kind_t kind);
 void mp_obj_exception_attr(mp_obj_t self_in, qstr attr, mp_obj_t *dest);
+mp_obj_exception_t *mp_obj_exception_get_native(mp_obj_t self_in);
 
 #define MP_DEFINE_EXCEPTION(exc_name, base_name) \
     const mp_obj_type_t mp_type_##exc_name = { \

shared-bindings/traceback/__init__.c

@@ -42,7 +42,6 @@ STATIC void traceback_exception_common(mp_print_t *print, mp_obj_t value, mp_obj
     if (!mp_obj_is_exception_instance(value)) {
         mp_raise_TypeError(translate("invalid exception"));
     }
-    mp_obj_exception_t exc = *(mp_obj_exception_t *)MP_OBJ_TO_PTR(value);
 
     mp_int_t limit = 0;
     bool print_tb = true;
@@ -51,13 +50,17 @@ STATIC void traceback_exception_common(mp_print_t *print, mp_obj_t value, mp_obj
         print_tb = (limit != 0);
     }
 
+    mp_obj_exception_t *exc = mp_obj_exception_get_native(value);
+    mp_obj_traceback_t *trace_backup = exc->traceback;
+
     if (tb_obj != mp_const_none && print_tb) {
-        exc.traceback = mp_arg_validate_type(tb_obj, &mp_type_traceback, MP_QSTR_tb);
+        exc->traceback = mp_arg_validate_type(tb_obj, &mp_type_traceback, MP_QSTR_tb);
     } else {
-        exc.traceback = (mp_obj_traceback_t *)&mp_const_empty_traceback_obj;
+        exc->traceback = (mp_obj_traceback_t *)&mp_const_empty_traceback_obj;
     }
 
-    shared_module_traceback_print_exception(&exc, print, limit);
+    shared_module_traceback_print_exception(MP_OBJ_TO_PTR(value), print, limit);
+    exc->traceback = trace_backup;
 }
 
 //| def format_exception(etype: Type[BaseException], value: BaseException, tb: TracebackType,