gh-126303: Fix pickling and copying of os.sched_param objects (GH-126336)

Author: serhiy-storchaka

Include/internal/pycore_typeobject.h

@@ -243,6 +243,7 @@ extern PyObject* _PyType_GetFullyQualifiedName(PyTypeObject *type, char sep);
 // self->tp_flags = (self->tp_flags & ~mask) | flags;
 extern void _PyType_SetFlags(PyTypeObject *self, unsigned long mask,
                              unsigned long flags);
+extern int _PyType_AddMethod(PyTypeObject *, PyMethodDef *);
 
 // Like _PyType_SetFlags(), but apply the operation to self and any of its
 // subclasses without Py_TPFLAGS_IMMUTABLETYPE set.

Lib/test/test_posix.py

@@ -6,12 +6,14 @@
 from test.support import warnings_helper
 from test.support.script_helper import assert_python_ok
 
+import copy
 import errno
 import sys
 import signal
 import time
 import os
 import platform
+import pickle
 import stat
 import tempfile
 import unittest
@@ -1317,6 +1319,25 @@ def test_get_and_set_scheduler_and_param(self):
         param = posix.sched_param(sched_priority=-large)
         self.assertRaises(OverflowError, posix.sched_setparam, 0, param)
 
+    @requires_sched
+    def test_sched_param(self):
+        param = posix.sched_param(1)
+        for proto in range(pickle.HIGHEST_PROTOCOL+1):
+            newparam = pickle.loads(pickle.dumps(param, proto))
+            self.assertEqual(newparam, param)
+        newparam = copy.copy(param)
+        self.assertIsNot(newparam, param)
+        self.assertEqual(newparam, param)
+        newparam = copy.deepcopy(param)
+        self.assertIsNot(newparam, param)
+        self.assertEqual(newparam, param)
+        newparam = copy.replace(param)
+        self.assertIsNot(newparam, param)
+        self.assertEqual(newparam, param)
+        newparam = copy.replace(param, sched_priority=0)
+        self.assertNotEqual(newparam, param)
+        self.assertEqual(newparam.sched_priority, 0)
+
     @unittest.skipUnless(hasattr(posix, "sched_rr_get_interval"), "no function")
     def test_sched_rr_get_interval(self):
         try:

Misc/NEWS.d/next/Library/2024-11-02-19-20-44.gh-issue-126303.yVvyWB.rst

@@ -0,0 +1 @@
+Fix pickling and copying of :class:`os.sched_param` objects.

Modules/posixmodule.c

@@ -24,6 +24,7 @@
 #include "pycore_pystate.h"       // _PyInterpreterState_GET()
 #include "pycore_signal.h"        // Py_NSIG
 #include "pycore_time.h"          // _PyLong_FromTime_t()
+#include "pycore_typeobject.h"    // _PyType_AddMethod()
 
 #ifdef HAVE_UNISTD_H
 #  include <unistd.h>             // symlink()
@@ -8210,6 +8211,16 @@ os_sched_param_impl(PyTypeObject *type, PyObject *sched_priority)
     return res;
 }
 
+static PyObject *
+os_sched_param_reduce(PyObject *self, PyObject *Py_UNUSED(ignored))
+{
+    return Py_BuildValue("(O(N))", Py_TYPE(self), PyStructSequence_GetItem(self, 0));
+}
+
+static PyMethodDef os_sched_param_reduce_method = {
+    "__reduce__", (PyCFunction)os_sched_param_reduce, METH_NOARGS|METH_COEXIST, NULL,
+};
+
 PyDoc_VAR(os_sched_param__doc__);
 
 static PyStructSequence_Field sched_param_fields[] = {
@@ -18033,6 +18044,12 @@ posixmodule_exec(PyObject *m)
         return -1;
     }
     ((PyTypeObject *)state->SchedParamType)->tp_new = os_sched_param;
+    if (_PyType_AddMethod((PyTypeObject *)state->SchedParamType,
+                          &os_sched_param_reduce_method) < 0)
+    {
+        return -1;
+    }
+    PyType_Modified((PyTypeObject *)state->SchedParamType);
 #endif
 
     /* initialize TerminalSize_info */

Objects/typeobject.c

@@ -7656,6 +7656,12 @@ type_add_method(PyTypeObject *type, PyMethodDef *meth)
     return 0;
 }
 
+int
+_PyType_AddMethod(PyTypeObject *type, PyMethodDef *meth)
+{
+    return type_add_method(type, meth);
+}
+
 
 /* Add the methods from tp_methods to the __dict__ in a type object */
 static int