StackRduino
diff --git a/‎py/objstrunicode.c‎
Lines changed: 9 additions & 6 deletions b/‎py/objstrunicode.c‎
Lines changed: 9 additions & 6 deletions
@@ -149,26 +149,29 @@ const byte *str_index_to_ptr(const mp_obj_type_t *type, const byte *self_data, s
             }
         }
         ++s;
-    } else if (!i) {
-        return self_data; // Shortcut - str[0] is its base pointer
     } else {
         // Positive indexing, correspondingly, counts from the start of the string.
         // It's assumed that negative indexing will generally be used with small
         // absolute values (eg str[-1], not str[-1000000]), which means it'll be
         // more efficient this way.
-        for (s = self_data; true; ++s) {
+        s = self_data;
+        while (1) {
+            // First check out-of-bounds
             if (s >= top) {
                 if (is_slice) {
                     return top;
                 }
                 nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_IndexError, "string index out of range"));
             }
+            // Then check completion
+            if (i-- == 0) {
+                break;
+            }
+            // Then skip UTF-8 char
+            ++s;
             while (UTF8_IS_CONT(*s)) {
                 ++s;
             }
-            if (!i--) {
-                return s;
-            }
         }
     }
     return s;
Original file line number	Diff line number	Diff line change
`@@ -149,26 +149,29 @@ const byte str_index_to_ptr(const mp_obj_type_t type, const byte *self_data, s`
`149`	`149`	`}`
`150`	`150`	`}`
`151`	`151`	`++s;`
`152`		`- } else if (!i) {`
`153`		`- return self_data; // Shortcut - str[0] is its base pointer`
`154`	`152`	`} else {`
`155`	`153`	`// Positive indexing, correspondingly, counts from the start of the string.`
`156`	`154`	`// It's assumed that negative indexing will generally be used with small`
`157`	`155`	`// absolute values (eg str[-1], not str[-1000000]), which means it'll be`
`158`	`156`	`// more efficient this way.`
`159`		`- for (s = self_data; true; ++s) {`
	`157`	`+ s = self_data;`
	`158`	`+ while (1) {`
	`159`	`+ // First check out-of-bounds`
`160`	`160`	`if (s >= top) {`
`161`	`161`	`if (is_slice) {`
`162`	`162`	`return top;`
`163`	`163`	`}`
`164`	`164`	`nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_IndexError, "string index out of range"));`
`165`	`165`	`}`
	`166`	`+ // Then check completion`
	`167`	`+ if (i-- == 0) {`
	`168`	`+ break;`
	`169`	`+ }`
	`170`	`+ // Then skip UTF-8 char`
	`171`	`+ ++s;`
`166`	`172`	`while (UTF8_IS_CONT(*s)) {`
`167`	`173`	`++s;`
`168`	`174`	`}`
`169`		`- if (!i--) {`
`170`		`- return s;`
`171`		`- }`
`172`	`175`	`}`
`173`	`176`	`}`
`174`	`177`	`return s;`