TechPenguineer · pull · May 28, 2025 · May 28, 2025 · May 28, 2025
diff --git a/Doc/whatsnew/3.15.rst b/Doc/whatsnew/3.15.rst
@@ -89,6 +89,13 @@ New modules
 Improved modules
 ================
 
+difflib
+-------
+
+* Improved the styling of HTML diff pages generated by the :class:`difflib.HtmlDiff`
+  class, and migrated the output to the HTML5 standard.
+  (Contributed by Jiahao Li in :gh:`134580`.)
+
 ssl
 ---
 

diff --git a/Include/internal/pycore_interp_structs.h b/Include/internal/pycore_interp_structs.h
@@ -677,8 +677,11 @@ struct _Py_interp_cached_objects {
 
     /* object.__reduce__ */
     PyObject *objreduce;
+#ifndef Py_GIL_DISABLED
+    /* resolve_slotdups() */
     PyObject *type_slots_pname;
     pytype_slotdef *type_slots_ptrs[MAX_EQUIV];
+#endif
 
     /* TypeVar and related types */
     PyTypeObject *generic_type;

diff --git a/Include/internal/pycore_object.h b/Include/internal/pycore_object.h
@@ -313,7 +313,7 @@ extern int _PyDict_CheckConsistency(PyObject *mp, int check_content);
 // Fast inlined version of PyType_HasFeature()
 static inline int
 _PyType_HasFeature(PyTypeObject *type, unsigned long feature) {
-    return ((FT_ATOMIC_LOAD_ULONG_RELAXED(type->tp_flags) & feature) != 0);
+    return ((type->tp_flags) & feature) != 0;
 }
 
 extern void _PyType_InitCache(PyInterpreterState *interp);

diff --git a/Include/internal/pycore_typeobject.h b/Include/internal/pycore_typeobject.h
@@ -134,7 +134,6 @@ extern int _PyType_AddMethod(PyTypeObject *, PyMethodDef *);
 extern void _PyType_SetFlagsRecursive(PyTypeObject *self, unsigned long mask,
                                       unsigned long flags);
 
-extern unsigned int _PyType_GetVersionForCurrentState(PyTypeObject *tp);
 PyAPI_FUNC(void) _PyType_SetVersion(PyTypeObject *tp, unsigned int version);
 PyTypeObject *_PyType_LookupByVersion(unsigned int version);
 

diff --git a/Include/object.h b/Include/object.h
@@ -620,6 +620,12 @@ given type object has a specified feature.
 #define Py_TPFLAGS_HAVE_FINALIZE (1UL << 0)
 #define Py_TPFLAGS_HAVE_VERSION_TAG   (1UL << 18)
 
+// Flag values for ob_flags (16 bits available, if SIZEOF_VOID_P > 4).
+#define _Py_IMMORTAL_FLAGS (1 << 0)
+#define _Py_STATICALLY_ALLOCATED_FLAG (1 << 2)
+#if defined(Py_GIL_DISABLED) && defined(Py_DEBUG)
+#define _Py_TYPE_REVEALED_FLAG (1 << 3)
+#endif
 
 #define Py_CONSTANT_NONE 0
 #define Py_CONSTANT_FALSE 1
@@ -776,11 +782,7 @@ PyType_HasFeature(PyTypeObject *type, unsigned long feature)
     // PyTypeObject is opaque in the limited C API
     flags = PyType_GetFlags(type);
 #else
-#   ifdef Py_GIL_DISABLED
-        flags = _Py_atomic_load_ulong_relaxed(&type->tp_flags);
-#   else
-        flags = type->tp_flags;
-#   endif
+    flags = type->tp_flags;
 #endif
     return ((flags & feature) != 0);
 }

diff --git a/Include/refcount.h b/Include/refcount.h
@@ -19,9 +19,6 @@ immortal. The latter should be the only instances that require
 cleanup during runtime finalization.
 */
 
-#define _Py_STATICALLY_ALLOCATED_FLAG 4
-#define _Py_IMMORTAL_FLAGS 1
-
 #if SIZEOF_VOID_P > 4
 /*
 In 64+ bit systems, any object whose 32 bit reference count is >= 2**31

diff --git a/Lib/difflib.py b/Lib/difflib.py
@@ -1615,16 +1615,13 @@ def _line_pair_iterator():
 
 
 _file_template = """
-<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
-          "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
-
-<html>
-
+<!DOCTYPE html>
+<html lang="en">
 <head>
-    <meta http-equiv="Content-Type"
-          content="text/html; charset=%(charset)s" />
-    <title></title>
-    <style type="text/css">%(styles)s
+    <meta charset="%(charset)s">
+    <meta name="viewport" content="width=device-width, initial-scale=1">
+    <title>Diff comparison</title>
+    <style>%(styles)s
     </style>
 </head>
 
@@ -1636,20 +1633,45 @@ def _line_pair_iterator():
 
 _styles = """
         :root {color-scheme: light dark}
-        table.diff {font-family: Menlo, Consolas, Monaco, Liberation Mono, Lucida Console, monospace; border:medium}
-        .diff_header {background-color:#e0e0e0}
-        td.diff_header {text-align:right}
-        .diff_next {background-color:#c0c0c0}
+        table.diff {
+            font-family: Menlo, Consolas, Monaco, Liberation Mono, Lucida Console, monospace;
+            border: medium;
+        }
+        .diff_header {
+            background-color: #e0e0e0;
+            font-weight: bold;
+        }
+        td.diff_header {
+            text-align: right;
+            padding: 0 8px;
+        }
+        .diff_next {
+            background-color: #c0c0c0;
+            padding: 4px 0;
+        }
         .diff_add {background-color:palegreen}
         .diff_chg {background-color:#ffff77}
         .diff_sub {background-color:#ffaaaa}
+        table.diff[summary="Legends"] {
+            margin-top: 20px;
+            border: 1px solid #ccc;
+        }
+        table.diff[summary="Legends"] th {
+            background-color: #e0e0e0;
+            padding: 4px 8px;
+        }
+        table.diff[summary="Legends"] td {
+            padding: 4px 8px;
+        }
 
         @media (prefers-color-scheme: dark) {
             .diff_header {background-color:#666}
             .diff_next {background-color:#393939}
             .diff_add {background-color:darkgreen}
             .diff_chg {background-color:#847415}
             .diff_sub {background-color:darkred}
+            table.diff[summary="Legends"] {border-color:#555}
+            table.diff[summary="Legends"] th{background-color:#666}
         }"""
 
 _table_template = """
@@ -1692,7 +1714,7 @@ class HtmlDiff(object):
     make_table -- generates HTML for a single side by side table
     make_file -- generates complete HTML file with a single side by side table
 
-    See tools/scripts/diff.py for an example usage of this class.
+    See Doc/includes/diff.py for an example usage of this class.
     """
 
     _file_template = _file_template

diff --git a/Lib/test/test_descr.py b/Lib/test/test_descr.py
@@ -4114,6 +4114,34 @@ class E(D):
         else:
             self.fail("shouldn't be able to create inheritance cycles")
 
+    def test_assign_bases_many_subclasses(self):
+        # This is intended to check that typeobject.c:queue_slot_update() can
+        # handle updating many subclasses when a slot method is re-assigned.
+        class A:
+            x = 'hello'
+            def __call__(self):
+                return 123
+            def __getitem__(self, index):
+                return None
+
+        class X:
+            x = 'bye'
+
+        class B(A):
+            pass
+
+        subclasses = []
+        for i in range(1000):
+            sc = type(f'Sub{i}', (B,), {})
+            subclasses.append(sc)
+
+        self.assertEqual(subclasses[0]()(), 123)
+        self.assertEqual(subclasses[0]().x, 'hello')
+        B.__bases__ = (X,)
+        with self.assertRaises(TypeError):
+            subclasses[0]()()
+        self.assertEqual(subclasses[0]().x, 'bye')
+
     def test_builtin_bases(self):
         # Make sure all the builtin types can have their base queried without
         # segfaulting. See issue #5787.

diff --git a/Lib/test/test_difflib.py b/Lib/test/test_difflib.py
@@ -255,21 +255,21 @@ def test_make_file_default_charset(self):
         html_diff = difflib.HtmlDiff()
         output = html_diff.make_file(patch914575_from1.splitlines(),
                                      patch914575_to1.splitlines())
-        self.assertIn('content="text/html; charset=utf-8"', output)
+        self.assertIn('charset="utf-8"', output)
 
     def test_make_file_iso88591_charset(self):
         html_diff = difflib.HtmlDiff()
         output = html_diff.make_file(patch914575_from1.splitlines(),
                                      patch914575_to1.splitlines(),
                                      charset='iso-8859-1')
-        self.assertIn('content="text/html; charset=iso-8859-1"', output)
+        self.assertIn('charset="iso-8859-1"', output)
 
     def test_make_file_usascii_charset_with_nonascii_input(self):
         html_diff = difflib.HtmlDiff()
         output = html_diff.make_file(patch914575_nonascii_from1.splitlines(),
                                      patch914575_nonascii_to1.splitlines(),
                                      charset='us-ascii')
-        self.assertIn('content="text/html; charset=us-ascii"', output)
+        self.assertIn('charset="us-ascii"', output)
         self.assertIn('&#305;mpl&#305;c&#305;t', output)
 
 class TestDiffer(unittest.TestCase):

diff --git a/Lib/test/test_difflib_expect.html b/Lib/test/test_difflib_expect.html
@@ -1,29 +1,51 @@
 
-<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
-          "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
-
-<html>
-
+<!DOCTYPE html>
+<html lang="en">
 <head>
-    <meta http-equiv="Content-Type"
-          content="text/html; charset=utf-8" />
-    <title></title>
-    <style type="text/css">
+    <meta charset="utf-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1">
+    <title>Diff comparison</title>
+    <style>
         :root {color-scheme: light dark}
-        table.diff {font-family: Menlo, Consolas, Monaco, Liberation Mono, Lucida Console, monospace; border:medium}
-        .diff_header {background-color:#e0e0e0}
-        td.diff_header {text-align:right}
-        .diff_next {background-color:#c0c0c0}
+        table.diff {
+            font-family: Menlo, Consolas, Monaco, Liberation Mono, Lucida Console, monospace;
+            border: medium;
+        }
+        .diff_header {
+            background-color: #e0e0e0;
+            font-weight: bold;
+        }
+        td.diff_header {
+            text-align: right;
+            padding: 0 8px;
+        }
+        .diff_next {
+            background-color: #c0c0c0;
+            padding: 4px 0;
+        }
         .diff_add {background-color:palegreen}
         .diff_chg {background-color:#ffff77}
         .diff_sub {background-color:#ffaaaa}
+        table.diff[summary="Legends"] {
+            margin-top: 20px;
+            border: 1px solid #ccc;
+        }
+        table.diff[summary="Legends"] th {
+            background-color: #e0e0e0;
+            padding: 4px 8px;
+        }
+        table.diff[summary="Legends"] td {
+            padding: 4px 8px;
+        }
 
         @media (prefers-color-scheme: dark) {
             .diff_header {background-color:#666}
             .diff_next {background-color:#393939}
             .diff_add {background-color:darkgreen}
             .diff_chg {background-color:#847415}
             .diff_sub {background-color:darkred}
+            table.diff[summary="Legends"] {border-color:#555}
+            table.diff[summary="Legends"] th{background-color:#666}
         }
     </style>
 </head>

diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2025-03-14-13-08-20.gh-issue-127266._tyfBp.rst b/Misc/NEWS.d/next/Core_and_Builtins/2025-03-14-13-08-20.gh-issue-127266._tyfBp.rst
@@ -0,0 +1,6 @@
+In the free-threaded build, avoid data races caused by updating type slots
+or type flags after the type was initially created.  For those (typically
+rare) cases, use the stop-the-world mechanism.  Remove the use of atomics
+when reading or writing type flags.  The use of atomics is not sufficient to
+avoid races (since flags are sometimes read without a lock and without
+atomics) and are no longer required.
diff --git a/Misc/NEWS.d/next/Library/2025-05-23-20-01-52.gh-issue-134580.xnaJ70.rst b/Misc/NEWS.d/next/Library/2025-05-23-20-01-52.gh-issue-134580.xnaJ70.rst
@@ -0,0 +1,3 @@
+Improved the styling of HTML diff pages generated by the
+:class:`difflib.HtmlDiff` class, and migrated the output to the HTML5
+standard.