Issue #5057: fix a bug in the peepholer that led to non-portable pyc files between narrow and wide builds while optimizing BINARY_SUBSCR on non-BMP chars (e.g. u"\U00012345"[0]).
diff --git a/Python/peephole.c b/Python/peephole.c
index 313eb43..433fe27 100644
--- a/Python/peephole.c
+++ b/Python/peephole.c
@@ -129,6 +129,24 @@
break;
case BINARY_SUBSCR:
newconst = PyObject_GetItem(v, w);
+ /* #5057: if v is unicode, there might be differences between
+ wide and narrow builds in cases like u'\U00012345'[0].
+ Wide builds will return a non-BMP char, whereas narrow builds
+ will return a surrogate. In both the cases skip the
+ optimization in order to produce compatible pycs.
+ */
+ if (newconst != NULL &&
+ PyUnicode_Check(v) && PyUnicode_Check(newconst)) {
+ Py_UNICODE ch = PyUnicode_AS_UNICODE(newconst)[0];
+#ifdef Py_UNICODE_WIDE
+ if (ch > 0xFFFF) {
+#else
+ if (ch >= 0xD800 && ch <= 0xDFFF) {
+#endif
+ Py_DECREF(newconst);
+ return 0;
+ }
+ }
break;
case BINARY_LSHIFT:
newconst = PyNumber_Lshift(v, w);