enable re-use of tuples in the free-threading build

python · colesbury · Aug 27, 2024 · Aug 23, 2024 · Aug 23, 2024 · Aug 23, 2024
commit 755a862c7e560b1b31c95a25e8bbe937389acc75
diff --git a/Include/refcount.h b/Include/refcount.h
@@ -493,6 +493,26 @@ static inline PyObject* _Py_XNewRef(PyObject *obj)
 #  define Py_XNewRef(obj) _Py_XNewRef(obj)
 #endif
 
+#ifdef Py_GIL_DISABLED
+static inline int _Py_Reuse_Immutable_Object(PyObject *ob) {
+    /* Function to check whether an immutable object such as a tuple can be
+     * modified inplace by the owning method
+     */
+    uint32_t local = _Py_atomic_load_uint32_relaxed(&ob->ob_ref_local);
+    if (local != 1)
+        return 0;
+    // maybe we need to check on Py_ARITHMETIC_RIGHT_SHIFT(Py_ssize_t, shared, _Py_REF_SHARED_SHIFT) ?
+    Py_ssize_t shared = _Py_atomic_load_ssize_relaxed(&ob->ob_ref_shared);
+    if (shared != 0) {
+        return 0;
+    }
+    return ob->ob_tid == _Py_ThreadId();
+}
+#else
+static inline int _Py_Reuse_Immutable_Object(PyObject *ob) {
+    return Py_REFCNT(ob) == 1;
+}
+#endif
 
 #ifdef __cplusplus
 }

@@ -2971,11 +2971,8 @@ zip_next(zipobject *lz)
 
     if (tuplesize == 0)
         return NULL;
-#ifdef Py_GIL_DISABLED
-    int reuse_tuple = 0;
- #else
-    int reuse_tuple = Py_REFCNT(result) == 1;
-#endif
+
+    int reuse_tuple = _Py_Reuse_Immutable_Object(result);
     if (reuse_tuple) {
         Py_INCREF(result);
         for (i=0 ; i < tuplesize ; i++) {