call PyUnicode_READY() during unicode indexing to comply with C-API constraints

Cython/Compiler/ExprNodes.py

@@ -10011,6 +10011,9 @@ proto = '''
                                                __Pyx_GetItemInt_Unicode_Generic(o, to_py_func(i)))
 
 static CYTHON_INLINE Py_UCS4 __Pyx_GetItemInt_Unicode_Fast(PyObject* ustring, Py_ssize_t i) {
+#if CYTHON_PEP393_ENABLED
+    if (unlikely(__Pyx_PyUnicode_READY(ustring) < 0)) return (Py_UCS4)-1;
+#endif
     const Py_ssize_t length = __Pyx_PyUnicode_GET_LENGTH(ustring);
     if (likely((0 <= i) & (i < length))) {
         return __Pyx_PyUnicode_READ_CHAR(ustring, i);
@@ -10029,6 +10032,12 @@ static CYTHON_INLINE Py_UCS4 __Pyx_GetItemInt_Unicode_Generic(PyObject* ustring,
     uchar_string = PyObject_GetItem(ustring, j);
     Py_DECREF(j);
     if (!uchar_string) return (Py_UCS4)-1;
+#if CYTHON_PEP393_ENABLED
+    if (unlikely(__Pyx_PyUnicode_READY(uchar_string) < 0)) {
+        Py_DECREF(uchar_string);
+        return (Py_UCS4)-1;
+    }
+#endif
     uchar = __Pyx_PyUnicode_READ_CHAR(uchar_string, 0);
     Py_DECREF(uchar_string);
     return uchar;

Cython/Utility/ModuleSetupCode.c

@@ -119,11 +119,14 @@
 /* new Py3.3 unicode type (PEP 393) */
 #if PY_VERSION_HEX > 0x03030000 && defined(PyUnicode_KIND)
   #define CYTHON_PEP393_ENABLED 1
+  #define __Pyx_PyUnicode_READY(op)       (likely(PyUnicode_IS_READY(op)) ? \
+                                              0 : _PyUnicode_Ready((PyObject *)(op)))
   #define __Pyx_PyUnicode_GET_LENGTH(u)   PyUnicode_GET_LENGTH(u)
   #define __Pyx_PyUnicode_READ_CHAR(u, i) PyUnicode_READ_CHAR(u, i)
   #define __Pyx_PyUnicode_READ(k, d, i)   PyUnicode_READ(k, d, i)
 #else
   #define CYTHON_PEP393_ENABLED 0
+  #define __Pyx_PyUnicode_READY(op)       (0)
   #define __Pyx_PyUnicode_GET_LENGTH(u)   PyUnicode_GET_SIZE(u)
   #define __Pyx_PyUnicode_READ_CHAR(u, i) ((Py_UCS4)(PyUnicode_AS_UNICODE(u)[i]))
   /* (k=k) => avoid unused variable warning due to macro: */

Cython/Utility/Optimize.c

@@ -428,7 +428,7 @@ static CYTHON_INLINE int __Pyx_init_unicode_iteration(
 static CYTHON_INLINE int __Pyx_init_unicode_iteration(
     PyObject* ustring, Py_ssize_t *length, void** data, int *kind) {
 #if CYTHON_PEP393_ENABLED
-    if (unlikely(PyUnicode_READY(ustring) < 0)) return -1;
+    if (unlikely(__Pyx_PyUnicode_READY(ustring) < 0)) return -1;
     *kind   = PyUnicode_KIND(ustring);
     *length = PyUnicode_GET_LENGTH(ustring);
     *data   = PyUnicode_DATA(ustring);