gh-115754: Use Py_GetConstant(Py_CONSTANT_EMPTY_BYTES)

Replace PyBytes_FromStringAndSize(NULL, 0)
with Py_GetConstant(Py_CONSTANT_EMPTY_BYTES).

Author: vstinner

Modules/_bz2module.c

@@ -664,7 +664,7 @@ _bz2_BZ2Decompressor_impl(PyTypeObject *type)
     self->bzs_avail_in_real = 0;
     self->input_buffer = NULL;
     self->input_buffer_size = 0;
-    self->unused_data = PyBytes_FromStringAndSize(NULL, 0);
+    self->unused_data = Py_GetConstant(Py_CONSTANT_EMPTY_BYTES);
     if (self->unused_data == NULL)
         goto error;
 

Modules/_datetimemodule.c

@@ -1747,7 +1747,7 @@ make_somezreplacement(PyObject *object, char *sep, PyObject *tzinfoarg)
     PyObject *tzinfo = get_tzinfo_member(object);
 
     if (tzinfo == Py_None || tzinfo == NULL) {
-        return PyBytes_FromStringAndSize(NULL, 0);
+        return Py_GetConstant(Py_CONSTANT_EMPTY_BYTES);
     }
 
     assert(tzinfoarg != NULL);

Modules/_dbmmodule.c

@@ -394,7 +394,7 @@ _dbm_dbm_setdefault_impl(dbmobject *self, PyTypeObject *cls, const char *key,
         return PyBytes_FromStringAndSize(val.dptr, val.dsize);
     }
     if (default_value == NULL) {
-        default_value = PyBytes_FromStringAndSize(NULL, 0);
+        default_value = Py_GetConstant(Py_CONSTANT_EMPTY_BYTES);
         if (default_value == NULL) {
             return NULL;
         }

Modules/_io/bufferedio.c

@@ -1030,7 +1030,7 @@ _io__Buffered_read1_impl(buffered *self, Py_ssize_t n)
     CHECK_CLOSED(self, "read of closed file")
 
     if (n == 0)
-        return PyBytes_FromStringAndSize(NULL, 0);
+        return Py_GetConstant(Py_CONSTANT_EMPTY_BYTES);
 
     /* Return up to n bytes.  If at least one byte is buffered, we
        only return buffered bytes.  Otherwise, we do one raw read. */

Modules/_io/bytesio.c

@@ -913,7 +913,7 @@ bytesio_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
     /* tp_alloc initializes all the fields to zero. So we don't have to
        initialize them here. */
 
-    self->buf = PyBytes_FromStringAndSize(NULL, 0);
+    self->buf = Py_GetConstant(Py_CONSTANT_EMPTY_BYTES);
     if (self->buf == NULL) {
         Py_DECREF(self);
         return PyErr_NoMemory();

Modules/_io/winconsoleio.c

@@ -874,7 +874,7 @@ _io__WindowsConsoleIO_readall_impl(winconsoleio *self)
     if (len == 0 && _buflen(self) == 0) {
         /* when the result starts with ^Z we return an empty buffer */
         PyMem_Free(buf);
-        return PyBytes_FromStringAndSize(NULL, 0);
+        return Py_GetConstant(Py_CONSTANT_EMPTY_BYTES);
     }
 
     if (len) {

Modules/_lzmamodule.c

@@ -1255,7 +1255,7 @@ _lzma_LZMADecompressor_impl(PyTypeObject *type, int format,
     self->needs_input = 1;
     self->input_buffer = NULL;
     self->input_buffer_size = 0;
-    Py_XSETREF(self->unused_data, PyBytes_FromStringAndSize(NULL, 0));
+    Py_XSETREF(self->unused_data, Py_GetConstant(Py_CONSTANT_EMPTY_BYTES));
     if (self->unused_data == NULL) {
         goto error;
     }

Modules/_sqlite/blob.c

@@ -191,7 +191,7 @@ blob_read_impl(pysqlite_Blob *self, int length)
 
     assert(length >= 0);
     if (length == 0) {
-        return PyBytes_FromStringAndSize(NULL, 0);
+        return Py_GetConstant(Py_CONSTANT_EMPTY_BYTES);
     }
 
     PyObject *buffer = read_multiple(self, length, self->offset);

Modules/cjkcodecs/multibytecodec.c

@@ -498,7 +498,7 @@ multibytecodec_encode(const MultibyteCodec *codec,
     datalen = PyUnicode_GET_LENGTH(text);
 
     if (datalen == 0 && !(flags & MBENC_RESET))
-        return PyBytes_FromStringAndSize(NULL, 0);
+        return Py_GetConstant(Py_CONSTANT_EMPTY_BYTES);
 
     buf.excobj = NULL;
     buf.outobj = NULL;

Modules/zlibmodule.c

@@ -990,7 +990,7 @@ zlib_Compress_flush_impl(compobject *self, PyTypeObject *cls, int mode)
     /* Flushing with Z_NO_FLUSH is a no-op, so there's no point in
        doing any work at all; just return an empty string. */
     if (mode == Z_NO_FLUSH) {
-        return PyBytes_FromStringAndSize(NULL, 0);
+        return Py_GetConstant(Py_CONSTANT_EMPTY_BYTES);
     }
 
     ENTER_ZLIB(self);
@@ -1739,7 +1739,7 @@ ZlibDecompressor__new__(PyTypeObject *cls,
     self->zst.zfree = PyZlib_Free;
     self->zst.next_in = NULL;
     self->zst.avail_in = 0;
-    self->unused_data = PyBytes_FromStringAndSize(NULL, 0);
+    self->unused_data = Py_GetConstant(Py_CONSTANT_EMPTY_BYTES);
     if (self->unused_data == NULL) {
         Py_CLEAR(self);
         return NULL;