Remove _PyByteArray_empty_string, add bytearray_reinit_from_bytes

De-duplicate the code to set `ob_bytes`, `ob_start`, `ob_alloc` and `ob_size`; rely in resize on ob_start being always set.
encukou · Nov 13, 2025 · Oct 3, 2025 · Oct 14, 2025 · Oct 3, 2025 · Oct 15, 2025
commit 99e49efa7dc3a57168766ea51c6adca754868576
diff --git a/Include/cpython/bytearrayobject.h b/Include/cpython/bytearrayobject.h
@@ -12,19 +12,13 @@ typedef struct {
     PyObject *ob_bytes_object;  /* PyBytes for zero-copy bytes conversion */
 } PyByteArrayObject;
 
-PyAPI_DATA(char) _PyByteArray_empty_string[];
-
 /* Macros and static inline functions, trading safety for speed */
 #define _PyByteArray_CAST(op) \
     (assert(PyByteArray_Check(op)), _Py_CAST(PyByteArrayObject*, op))
 
 static inline char* PyByteArray_AS_STRING(PyObject *op)
 {
-    PyByteArrayObject *self = _PyByteArray_CAST(op);
-    if (Py_SIZE(self)) {
-        return self->ob_start;
-    }
-    return _PyByteArray_empty_string;
+    return _PyByteArray_CAST(op)->ob_start;
 }
 #define PyByteArray_AS_STRING(self) PyByteArray_AS_STRING(_PyObject_CAST(self))
 

diff --git a/Objects/bytearrayobject.c b/Objects/bytearrayobject.c
@@ -17,9 +17,6 @@ class bytearray "PyByteArrayObject *" "&PyByteArray_Type"
 [clinic start generated code]*/
 /*[clinic end generated code: output=da39a3ee5e6b4b0d input=5535b77c37a119e0]*/
 
-/* For PyByteArray_AS_STRING(). */
-char _PyByteArray_empty_string[] = "";
-
 /* Max number of bytes a bytearray can contain */
 #define PyByteArray_SIZE_MAX ((Py_ssize_t)(PY_SSIZE_T_MAX - _PyBytesObject_SIZE))
 
@@ -46,6 +43,14 @@ _getbytevalue(PyObject* arg, int *value)
     return 1;
 }
 
+static void
+bytearray_reinit_from_bytes(PyByteArrayObject *self, Py_ssize_t size,
+                            Py_ssize_t alloc) {
+    self->ob_bytes = self->ob_start = PyBytes_AS_STRING(self->ob_bytes_object);
+    Py_SET_SIZE(self, size);
+    FT_ATOMIC_STORE_SSIZE_RELAXED(self->ob_alloc, alloc);
+}
+
 static int
 bytearray_getbuffer_lock_held(PyObject *self, Py_buffer *view, int flags)
 {
@@ -151,14 +156,10 @@ PyByteArray_FromStringAndSize(const char *bytes, Py_ssize_t size)
         Py_DECREF(new);
         return NULL;
     }
-    new->ob_bytes = PyBytes_AS_STRING(new->ob_bytes_object);
-    assert(new->ob_bytes);
+    bytearray_reinit_from_bytes(new, size, size);
     if (bytes != NULL && size > 0) {
         memcpy(new->ob_bytes, bytes, size);
     }
-    Py_SET_SIZE(new, size);
-    new->ob_alloc = size;
-    new->ob_start = new->ob_bytes;
     new->ob_exports = 0;
 
     return (PyObject *)new;
@@ -247,26 +248,12 @@ bytearray_resize_lock_held(PyObject *self, Py_ssize_t requested_size)
                 Py_MIN(requested_size, Py_SIZE(self)));
     }
 
-    if (obj->ob_bytes_object == NULL) {
-        obj->ob_bytes_object = PyBytes_FromStringAndSize(NULL, alloc);
-    }
-    else {
-        _PyBytes_Resize(&obj->ob_bytes_object, alloc);
-    }
-
-    int ret;
-    if (obj->ob_bytes_object == NULL) {
+    int ret = _PyBytes_Resize(&obj->ob_bytes_object, alloc);
+    if (ret == -1) {
         obj->ob_bytes_object = Py_GetConstant(Py_CONSTANT_EMPTY_BYTES);
         size = alloc = 0;
-        ret = -1;
     }
-    else {
-        ret = 0;
-    }
-
-    obj->ob_bytes = obj->ob_start = PyBytes_AS_STRING(obj->ob_bytes_object);
-    Py_SET_SIZE(self, size);
-    FT_ATOMIC_STORE_SSIZE_RELAXED(obj->ob_alloc, alloc);
+    bytearray_reinit_from_bytes(obj, size, alloc);
     if (alloc != size) {
         /* Add mid-buffer null; end provided by bytes. */
         obj->ob_bytes[size] = '\0';
@@ -904,6 +891,13 @@ bytearray___init___impl(PyByteArrayObject *self, PyObject *arg,
     PyObject *it;
     PyObject *(*iternext)(PyObject *);
 
+    /* First __init__; set ob_bytes_object so ob_bytes is always non-null. */
+    if (self->ob_bytes_object == NULL) {
+        self->ob_bytes_object = Py_GetConstant(Py_CONSTANT_EMPTY_BYTES);
+        bytearray_reinit_from_bytes(self, 0, 0);
+        self->ob_exports = 0;
+    }
+
     if (Py_SIZE(self) != 0) {
         /* Empty previous contents (yes, do this first of all!) */
         if (PyByteArray_Resize((PyObject *)self, 0) < 0)
@@ -1564,9 +1558,7 @@ bytearray_take_bytes_impl(PyByteArrayObject *self, PyObject *n)
     // Point the bytearray towards the buffer with the remaining data.
     PyObject *result = self->ob_bytes_object;
     self->ob_bytes_object = remaining;
-    self->ob_bytes = self->ob_start = PyBytes_AS_STRING(self->ob_bytes_object);
-    Py_SET_SIZE(self, remaining_length);
-    FT_ATOMIC_STORE_SSIZE_RELAXED(self->ob_alloc, remaining_length);
+    bytearray_reinit_from_bytes(self, remaining_length, remaining_length);
     return result;
 }
 

diff --git a/Tools/c-analyzer/cpython/ignored.tsv b/Tools/c-analyzer/cpython/ignored.tsv
@@ -324,7 +324,6 @@ Modules/pyexpat.c	-	error_info_of	-
 Modules/pyexpat.c	-	handler_info	-
 Modules/termios.c	-	termios_constants	-
 Modules/timemodule.c	init_timezone	YEAR	-
-Objects/bytearrayobject.c	-	_PyByteArray_empty_string	-
 Objects/complexobject.c	-	c_1	-
 Objects/exceptions.c	-	static_exceptions	-
 Objects/genobject.c	-	ASYNC_GEN_IGNORED_EXIT_MSG	-