Force alignment of empty bytearray and array.array buffers

This ensures the buffers used by the empty `bytearray` and `array.array`
are aligned the same as a pointer returned by the allocator.  This is a
more convenient default for interop with other languages that have
stricter requirements of type-safe buffers (e.g. Rust's `&[T]` type)
even when empty.

Author: jakelishman

Misc/ACKS

@@ -1148,6 +1148,7 @@ Per Lindqvist
 Eric Lindvall
 Gregor Lingl
 Everett Lipman
+Jake Lishman
 Mirko Liss
 Alexander Liu
 Hui Liu

Misc/NEWS.d/next/Core_and_Builtins/2025-10-24-17-30-51.gh-issue-140557.X2GETk.rst

@@ -0,0 +1,3 @@
+The empty instances of :func:`bytearray` and :func:`array.array` now produce
+buffers that are aligned for any data type.  This is a convenience for
+interoperation with other languages.

Modules/arraymodule.c

@@ -2655,7 +2655,7 @@ array_ass_subscr(PyObject *op, PyObject *item, PyObject *value)
     }
 }
 
-static const void *emptybuf = "";
+static const _Py_ALIGNED_DEF(ALIGNOF_MAX_ALIGN_T, char) emptybuf[] = "";
 
 
 static int

Objects/bytearrayobject.c

@@ -18,7 +18,7 @@ class bytearray "PyByteArrayObject *" "&PyByteArray_Type"
 /*[clinic end generated code: output=da39a3ee5e6b4b0d input=5535b77c37a119e0]*/
 
 /* For PyByteArray_AS_STRING(). */
-char _PyByteArray_empty_string[] = "";
+_Py_ALIGNED_DEF(ALIGNOF_MAX_ALIGN_T, char) _PyByteArray_empty_string[] = "";
 
 /* Helpers */