traceback: fix for crash on non-native exceptions

microdev1 · timhawes · microdev1 · commit 70b3e73349cd · 2021-12-15T12:29:21.000+05:30
Co-authored-by: Tim Hawes &lt;me@timhawes.com&gt;
diff --git a/py/objexcept.c b/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;
diff --git a/py/objexcept.h b/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 = { \
diff --git a/shared-bindings/traceback/__init__.c b/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,

Original file line number	Diff line number	Diff line change
`@@ -42,7 +42,6 @@ STATIC void traceback_exception_common(mp_print_t *print, mp_obj_t value, mp_obj`
`42`	`42`	`if (!mp_obj_is_exception_instance(value)) {`
`43`	`43`	`mp_raise_TypeError(translate("invalid exception"));`
`44`	`44`	`}`
`45`		`- mp_obj_exception_t exc = (mp_obj_exception_t )MP_OBJ_TO_PTR(value);`
`46`	`45`
`47`	`46`	`mp_int_t limit = 0;`
`48`	`47`	`bool print_tb = true;`
`@@ -51,13 +50,17 @@ STATIC void traceback_exception_common(mp_print_t *print, mp_obj_t value, mp_obj`
`51`	`50`	`print_tb = (limit != 0);`
`52`	`51`	`}`
`53`	`52`
	`53`	`+ mp_obj_exception_t *exc = mp_obj_exception_get_native(value);`
	`54`	`+ mp_obj_traceback_t *trace_backup = exc->traceback;`
	`55`	`+`
`54`	`56`	`if (tb_obj != mp_const_none && print_tb) {`
`55`		`- exc.traceback = mp_arg_validate_type(tb_obj, &mp_type_traceback, MP_QSTR_tb);`
	`57`	`+ exc->traceback = mp_arg_validate_type(tb_obj, &mp_type_traceback, MP_QSTR_tb);`
`56`	`58`	`} else {`
`57`		`- exc.traceback = (mp_obj_traceback_t *)&mp_const_empty_traceback_obj;`
	`59`	`+ exc->traceback = (mp_obj_traceback_t *)&mp_const_empty_traceback_obj;`
`58`	`60`	`}`
`59`	`61`
`60`		`- shared_module_traceback_print_exception(&exc, print, limit);`
	`62`	`+ shared_module_traceback_print_exception(MP_OBJ_TO_PTR(value), print, limit);`
	`63`	`+ exc->traceback = trace_backup;`
`61`	`64`	`}`
`62`	`65`
`63`	`66`	`//\| def format_exception(etype: Type[BaseException], value: BaseException, tb: TracebackType,`