Merge remote-tracking branch 'upstream/main' into opt_guard_code_version

Author: Fidget-Spinner

Lib/encodings/__init__.py

@@ -34,6 +34,7 @@
 from . import aliases
 
 _cache = {}
+_MAXCACHE = 500
 _unknown = '--unknown--'
 _import_tail = ['*']
 _aliases = aliases.aliases
@@ -111,6 +112,8 @@ def search_function(encoding):
 
     if mod is None:
         # Cache misses
+        if len(_cache) >= _MAXCACHE:
+            _cache.clear()
         _cache[encoding] = None
         return None
 
@@ -132,6 +135,8 @@ def search_function(encoding):
         entry = codecs.CodecInfo(*entry)
 
     # Cache the codec registry entry
+    if len(_cache) >= _MAXCACHE:
+        _cache.clear()
     _cache[encoding] = entry
 
     # Register its aliases (without overwriting previously registered

Lib/test/test_capi/test_opt.py

@@ -3984,6 +3984,22 @@ def testfunc(n):
         self.assertIn("_POP_TOP_NOP", uops)
         self.assertLessEqual(count_ops(ex, "_POP_TOP"), 2)
 
+    def test_iter_check_list(self):
+        def testfunc(n):
+            x = 0
+            for _ in range(n):
+                l = [1]
+                for num in l: # unguarded
+                    x += num
+            return x
+
+        res, ex = self._run_with_optimizer(testfunc, TIER2_THRESHOLD)
+        self.assertEqual(res, TIER2_THRESHOLD)
+        uops = get_opnames(ex)
+
+        self.assertIn("_BUILD_LIST", uops)
+        self.assertNotIn("_ITER_CHECK_LIST", uops)
+
     def test_match_class(self):
         def testfunc(n):
             class A:

Lib/test/test_codecs.py

@@ -3908,5 +3908,16 @@ def test_encodings_normalize_encoding(self):
             self.assertEqual(normalize('utf\xE9\u20AC\U0010ffff-8'), 'utf_8')
 
 
+class CodecCacheTest(unittest.TestCase):
+    def test_cache_bounded(self):
+        for i in range(encodings._MAXCACHE + 1000):
+            try:
+                b'x'.decode(f'nonexist_{i}')
+            except LookupError:
+                pass
+
+        self.assertLessEqual(len(encodings._cache), encodings._MAXCACHE)
+
+
 if __name__ == "__main__":
     unittest.main()

Misc/NEWS.d/next/Core_and_Builtins/2026-02-08-01-19-50.gh-issue-131798.PaWDNH.rst

@@ -0,0 +1 @@
+Optimize ``_ITER_CHECK_RANGE`` and ``_ITER_CHECK_LIST`` in the JIT

Misc/NEWS.d/next/Library/2026-03-17-11-46-20.gh-issue-146054.udYcqn.rst

@@ -0,0 +1,2 @@
+Limit the size of :func:`encodings.search_function` cache.
+Found by OSS Fuzz in :oss-fuzz:`493449985`.

Python/optimizer_bytecodes.c

@@ -1095,6 +1095,24 @@ dummy_func(void) {
         sym_set_type(iter, &PyTuple_Type);
     }
 
+    op(_ITER_CHECK_LIST, (iter, null_or_index -- iter, null_or_index)) {
+        if (sym_matches_type(iter, &PyList_Type)) {
+            ADD_OP(_NOP, 0, 0);
+        }
+        else {
+            sym_set_type(iter, &PyList_Type);
+        }
+    }
+
+    op(_ITER_CHECK_RANGE, (iter, null_or_index -- iter, null_or_index)) {
+        if (sym_matches_type(iter, &PyRange_Type)) {
+            ADD_OP(_NOP, 0, 0);
+        }
+        else {
+            sym_set_type(iter, &PyRange_Type);
+        }
+    }
+
     op(_ITER_NEXT_RANGE, (iter, null_or_index -- iter, null_or_index, next)) {
        next = sym_new_type(ctx, &PyLong_Type);
     }