pythongh-115754: Use Py_GetConstant(Py_CONSTANT_EMPTY_STR)

Replace PyUnicode_New(0, 0) with Py_GetConstant(Py_CONSTANT_EMPTY_STR).

Author: vstinner

Modules/_ctypes/_ctypes.c

@@ -4756,7 +4756,7 @@ Array_subscript(PyObject *myself, PyObject *item)
             wchar_t *dest;
 
             if (slicelen <= 0)
-                return PyUnicode_New(0, 0);
+                return Py_GetConstant(Py_CONSTANT_EMPTY_STR);
             if (step == 1) {
                 return PyUnicode_FromWideChar(ptr + start,
                                               slicelen);
@@ -5438,7 +5438,7 @@ Pointer_subscript(PyObject *myself, PyObject *item)
             wchar_t *dest;
 
             if (len <= 0)
-                return PyUnicode_New(0, 0);
+                return Py_GetConstant(Py_CONSTANT_EMPTY_STR);
             if (step == 1) {
                 return PyUnicode_FromWideChar(ptr + start,
                                               len);

Modules/_elementtree.c

@@ -1317,7 +1317,7 @@ _elementtree_Element_findtext_impl(ElementObject *self, PyTypeObject *cls,
             PyObject* text = element_get_text((ElementObject*)item);
             if (text == Py_None) {
                 Py_DECREF(item);
-                return PyUnicode_New(0, 0);
+                return Py_GetConstant(Py_CONSTANT_EMPTY_STR);
             }
             Py_XINCREF(text);
             Py_DECREF(item);

Modules/_io/stringio.c

@@ -353,7 +353,7 @@ _stringio_readline(stringio *self, Py_ssize_t limit)
 
     /* In case of overseek, return the empty string */
     if (self->pos >= self->string_size)
-        return PyUnicode_New(0, 0);
+        return Py_GetConstant(Py_CONSTANT_EMPTY_STR);
 
     start = self->buf + self->pos;
     if (limit < 0 || limit > self->string_size - self->pos)

Modules/cjkcodecs/multibytecodec.c

@@ -669,7 +669,7 @@ _multibytecodec_MultibyteCodec_decode_impl(MultibyteCodecObject *self,
 
     if (datalen == 0) {
         ERROR_DECREF(errorcb);
-        return make_tuple(PyUnicode_New(0, 0), 0);
+        return make_tuple(Py_GetConstant(Py_CONSTANT_EMPTY_STR), 0);
     }
 
     _PyUnicodeWriter_Init(&buf.writer);
@@ -1434,7 +1434,7 @@ mbstreamreader_iread(MultibyteStreamReaderObject *self,
     Py_ssize_t rsize;
 
     if (sizehint == 0)
-        return PyUnicode_New(0, 0);
+        return Py_GetConstant(Py_CONSTANT_EMPTY_STR);
 
     _PyUnicodeWriter_Init(&buf.writer);
     buf.excobj = NULL;

Modules/socketmodule.c

@@ -5636,7 +5636,7 @@ socket_gethostname(PyObject *self, PyObject *unused)
         return PyErr_SetFromWindowsErr(0);
 
     if (size == 0)
-        return PyUnicode_New(0, 0);
+        return Py_GetConstant(Py_CONSTANT_EMPTY_STR);
 
     /* MSDN says ERROR_MORE_DATA may occur because DNS allows longer
        names */

Objects/abstract.c

@@ -862,7 +862,7 @@ PyObject_Format(PyObject *obj, PyObject *format_spec)
 
     /* If no format_spec is provided, use an empty string */
     if (format_spec == NULL) {
-        empty = PyUnicode_New(0, 0);
+        empty = Py_GetConstant(Py_CONSTANT_EMPTY_STR);
         format_spec = empty;
     }
 

Objects/stringlib/unicode_format.h

@@ -73,7 +73,7 @@ Py_LOCAL_INLINE(PyObject *)
 SubString_new_object_or_empty(SubString *str)
 {
     if (str->str == NULL) {
-        return PyUnicode_New(0, 0);
+        return Py_GetConstant(Py_CONSTANT_EMPTY_STR);
     }
     return SubString_new_object(str);
 }
@@ -531,7 +531,7 @@ render_field(PyObject *fieldobj, SubString *format_spec, _PyUnicodeWriter *write
                                                      format_spec->start,
                                                      format_spec->end);
         else
-            format_spec_object = PyUnicode_New(0, 0);
+            format_spec_object = Py_GetConstant(Py_CONSTANT_EMPTY_STR);
         if (format_spec_object == NULL)
             goto done;
 

Python/codecs.c

@@ -696,7 +696,7 @@ PyObject *PyCodec_IgnoreErrors(PyObject *exc)
         wrong_exception_type(exc);
         return NULL;
     }
-    return Py_BuildValue("(Nn)", PyUnicode_New(0, 0), end);
+    return Py_BuildValue("(Nn)", Py_GetConstant(Py_CONSTANT_EMPTY_STR), end);
 }
 
 

Python/formatter_unicode.c

@@ -740,7 +740,7 @@ get_locale_info(enum LocaleType type, LocaleInfo *locale_info)
         break;
     case LT_NO_LOCALE:
         locale_info->decimal_point = PyUnicode_FromOrdinal('.');
-        locale_info->thousands_sep = PyUnicode_New(0, 0);
+        locale_info->thousands_sep = Py_GetConstant(Py_CONSTANT_EMPTY_STR);
         if (!locale_info->decimal_point || !locale_info->thousands_sep)
             return -1;
         locale_info->grouping = no_grouping;

Python/marshal.c

@@ -1218,7 +1218,7 @@ r_object(RFILE *p)
             v = PyUnicode_DecodeUTF8(buffer, n, "surrogatepass");
         }
         else {
-            v = PyUnicode_New(0, 0);
+            v = Py_GetConstant(Py_CONSTANT_EMPTY_STR);
         }
         if (v == NULL)
             break;