py/objstr: startswith, endswith: Check arg to be a string.

Otherwise, it will silently get incorrect result on other values types,
including CPython tuple form like "foo.png".endswith(("png", "jpg"))
(which MicroPython doesn't support for unbloatedness).

1 files changed, 4 insertions, 2 deletions

diff --git a/py/objstr.c b/py/objstr.c
index d4c038a68..f04bd90be 100644
--- a/py/objstr.c
+++ b/py/objstr.c
@@ -726,7 +726,8 @@ MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(str_rindex_obj, 2, 4, str_rindex);
 STATIC mp_obj_t str_startswith(size_t n_args, const mp_obj_t *args) {
     const mp_obj_type_t *self_type = mp_obj_get_type(args[0]);
     GET_STR_DATA_LEN(args[0], str, str_len);
-    GET_STR_DATA_LEN(args[1], prefix, prefix_len);
+    size_t prefix_len;
+    const char *prefix = mp_obj_str_get_data(args[1], &prefix_len);
     const byte *start = str;
     if (n_args > 2) {
         start = str_index_to_ptr(self_type, str, str_len, args[2], true);
@@ -740,7 +741,8 @@ MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(str_startswith_obj, 2, 3, str_startswith);
 
 STATIC mp_obj_t str_endswith(size_t n_args, const mp_obj_t *args) {
     GET_STR_DATA_LEN(args[0], str, str_len);
-    GET_STR_DATA_LEN(args[1], suffix, suffix_len);
+    size_t suffix_len;
+    const char *suffix = mp_obj_str_get_data(args[1], &suffix_len);
     if (n_args > 2) {
         mp_raise_NotImplementedError("start/end indices");
     }