gh-140009: Replace PyTuple_Pack with PyTuple_FromArray in codeobject.c and _pickle.c

Author: RoryGlenn

Misc/NEWS.d/next/Core_and_Builtins/2026-02-15-02-51-59.gh-issue-140009.Da1nxk.rst

@@ -0,0 +1,3 @@
+Replace :c:func:`PyTuple_Pack` calls with :c:func:`PyTuple_FromArray` in
+:file:`Objects/codeobject.c` and :file:`Modules/_pickle.c` to avoid
+variadic argument overhead.

Modules/_pickle.c

@@ -3758,7 +3758,8 @@ fix_imports(PickleState *st, PyObject **module_name, PyObject **global_name)
     PyObject *key;
     PyObject *item;
 
-    key = PyTuple_Pack(2, *module_name, *global_name);
+    PyObject *key_items[] = {*module_name, *global_name};
+    key = PyTuple_FromArray(key_items, 2);
     if (key == NULL)
         return -1;
     item = PyDict_GetItemWithError(st->name_mapping_3to2, key);
@@ -3864,7 +3865,8 @@ save_global(PickleState *st, PicklerObject *self, PyObject *obj,
         char pdata[5];
         Py_ssize_t n;
 
-        extension_key = PyTuple_Pack(2, module_name, global_name);
+        PyObject *ext_key_items[] = {module_name, global_name};
+        extension_key = PyTuple_FromArray(ext_key_items, 2);
         if (extension_key == NULL) {
             goto error;
         }
@@ -7307,7 +7309,8 @@ _pickle_Unpickler_find_class_impl(UnpicklerObject *self, PyTypeObject *cls,
 
         /* Check if the global (i.e., a function or a class) was renamed
            or moved to another module. */
-        key = PyTuple_Pack(2, module_name, global_name);
+        PyObject *find_key_items[] = {module_name, global_name};
+        key = PyTuple_FromArray(find_key_items, 2);
         if (key == NULL)
             return NULL;
         item = PyDict_GetItemWithError(st->name_mapping_2to3, key);

Objects/codeobject.c

@@ -2967,17 +2967,22 @@ _PyCode_ConstantKey(PyObject *op)
     else if (PyBool_Check(op) || PyBytes_CheckExact(op)) {
         /* Make booleans different from integers 0 and 1.
          * Avoid BytesWarning from comparing bytes with strings. */
-        key = PyTuple_Pack(2, Py_TYPE(op), op);
+        PyObject *items[] = {(PyObject *)Py_TYPE(op), op};
+        key = PyTuple_FromArray(items, 2);
     }
     else if (PyFloat_CheckExact(op)) {
         double d = PyFloat_AS_DOUBLE(op);
         /* all we need is to make the tuple different in either the 0.0
          * or -0.0 case from all others, just to avoid the "coercion".
          */
-        if (d == 0.0 && copysign(1.0, d) < 0.0)
-            key = PyTuple_Pack(3, Py_TYPE(op), op, Py_None);
-        else
-            key = PyTuple_Pack(2, Py_TYPE(op), op);
+        if (d == 0.0 && copysign(1.0, d) < 0.0) {
+            PyObject *items[] = {(PyObject *)Py_TYPE(op), op, Py_None};
+            key = PyTuple_FromArray(items, 3);
+        }
+        else {
+            PyObject *items[] = {(PyObject *)Py_TYPE(op), op};
+            key = PyTuple_FromArray(items, 2);
+        }
     }
     else if (PyComplex_CheckExact(op)) {
         Py_complex z;
@@ -2992,16 +2997,20 @@ _PyCode_ConstantKey(PyObject *op)
         /* use True, False and None singleton as tags for the real and imag
          * sign, to make tuples different */
         if (real_negzero && imag_negzero) {
-            key = PyTuple_Pack(3, Py_TYPE(op), op, Py_True);
+            PyObject *items[] = {(PyObject *)Py_TYPE(op), op, Py_True};
+            key = PyTuple_FromArray(items, 3);
         }
         else if (imag_negzero) {
-            key = PyTuple_Pack(3, Py_TYPE(op), op, Py_False);
+            PyObject *items[] = {(PyObject *)Py_TYPE(op), op, Py_False};
+            key = PyTuple_FromArray(items, 3);
         }
         else if (real_negzero) {
-            key = PyTuple_Pack(3, Py_TYPE(op), op, Py_None);
+            PyObject *items[] = {(PyObject *)Py_TYPE(op), op, Py_None};
+            key = PyTuple_FromArray(items, 3);
         }
         else {
-            key = PyTuple_Pack(2, Py_TYPE(op), op);
+            PyObject *items[] = {(PyObject *)Py_TYPE(op), op};
+            key = PyTuple_FromArray(items, 2);
         }
     }
     else if (PyTuple_CheckExact(op)) {
@@ -3026,7 +3035,8 @@ _PyCode_ConstantKey(PyObject *op)
             PyTuple_SET_ITEM(tuple, i, item_key);
         }
 
-        key = PyTuple_Pack(2, tuple, op);
+        PyObject *tuple_items[] = {tuple, op};
+        key = PyTuple_FromArray(tuple_items, 2);
         Py_DECREF(tuple);
     }
     else if (PyFrozenSet_CheckExact(op)) {
@@ -3060,7 +3070,8 @@ _PyCode_ConstantKey(PyObject *op)
         if (set == NULL)
             return NULL;
 
-        key = PyTuple_Pack(2, set, op);
+        PyObject *set_items[] = {set, op};
+        key = PyTuple_FromArray(set_items, 2);
         Py_DECREF(set);
         return key;
     }
@@ -3091,7 +3102,8 @@ _PyCode_ConstantKey(PyObject *op)
             goto slice_exit;
         }
 
-        key = PyTuple_Pack(2, slice_key, op);
+        PyObject *slice_items[] = {slice_key, op};
+        key = PyTuple_FromArray(slice_items, 2);
         Py_DECREF(slice_key);
     slice_exit:
         Py_XDECREF(start_key);
@@ -3105,7 +3117,8 @@ _PyCode_ConstantKey(PyObject *op)
         if (obj_id == NULL)
             return NULL;
 
-        key = PyTuple_Pack(2, obj_id, op);
+        PyObject *id_items[] = {obj_id, op};
+        key = PyTuple_FromArray(id_items, 2);
         Py_DECREF(obj_id);
     }
     return key;