Rename new macros to conform to naming rules (function macros have "Py" prefix, not "PY").
diff --git a/Modules/arraymodule.c b/Modules/arraymodule.c
index 9d49a97..90ca7c6 100644
--- a/Modules/arraymodule.c
+++ b/Modules/arraymodule.c
@@ -2810,7 +2810,7 @@
 PyInit_array(void)
 {
     PyObject *m;
-    char buffer[PY_ARRAY_LENGTH(descriptors)], *p;
+    char buffer[Py_ARRAY_LENGTH(descriptors)], *p;
     PyObject *typecodes;
     Py_ssize_t size = 0;
     struct arraydescr *descr;