[3.13] gh-130851: Don't crash when deduping unusual code constants (GH-130853)

Lib/test/test_code.py

@@ -596,6 +596,23 @@ def func2():
 
         self.assertTrue(globals["func1"]() is globals["func2"]())
 
+    @cpython_only
+    def test_unusual_constants(self):
+        # gh-130851: Code objects constructed with constants that are not
+        # types generated by the bytecode compiler should not crash the
+        # interpreter.
+        class Unhashable:
+            def __hash__(self):
+                raise TypeError("unhashable type")
+
+        class MyInt(int):
+            pass
+
+        code = compile("a = 1", "<string>", "exec")
+        code = code.replace(co_consts=(1, Unhashable(), MyInt(1), MyInt(1)))
+        self.assertIsInstance(code.co_consts[1], Unhashable)
+        self.assertEqual(code.co_consts[2], code.co_consts[3])
+
 
 class CodeWeakRefTest(unittest.TestCase):
 

Misc/NEWS.d/next/Core_and_Builtins/2025-03-04-20-33-28.gh-issue-130851.MT9j7n.rst

@@ -0,0 +1,3 @@
+Fix a crash in the :term:`free threading` build when constructing a
+:class:`code` object with :attr:`~codeobject.co_consts` that contains instances
+of types that are not otherwise generated by the bytecode compiler.

Objects/codeobject.c

@@ -2527,6 +2527,7 @@ intern_one_constant(PyObject *op)
     _Py_hashtable_entry_t *entry = _Py_hashtable_get_entry(consts, op);
     if (entry == NULL) {
         if (_Py_hashtable_set(consts, op, op) != 0) {
+            PyErr_NoMemory();
             return NULL;
         }
 
@@ -2548,7 +2549,8 @@ intern_one_constant(PyObject *op)
 }
 
 static int
-compare_constants(const void *key1, const void *key2) {
+compare_constants(const void *key1, const void *key2)
+{
     PyObject *op1 = (PyObject *)key1;
     PyObject *op2 = (PyObject *)key2;
     if (op1 == op2) {
@@ -2608,8 +2610,8 @@ compare_constants(const void *key1, const void *key2) {
         Py_complex c2 = ((PyComplexObject *)op2)->cval;
         return memcmp(&c1, &c2, sizeof(Py_complex)) == 0;
     }
-    _Py_FatalErrorFormat("unexpected type in compare_constants: %s",
-                         Py_TYPE(op1)->tp_name);
+    // gh-130851: Treat instances of unexpected types as distinct if they are
+    // not the same object.
     return 0;
 }
 
@@ -2629,9 +2631,13 @@ hash_const(const void *key)
     }
     Py_hash_t h = PyObject_Hash(op);
     if (h == -1) {
-        // This should never happen: all the constants we support have
-        // infallible hash functions.
-        Py_FatalError("code: hash failed");
+        // gh-130851: Other than slice objects, every constant that the
+        // bytecode compiler generates is hashable. However, users can
+        // provide their own constants, when constructing code objects via
+        // types.CodeType(). If the user-provided constant is unhashable, we
+        // use the memory address of the object as a fallback hash value.
+        PyErr_Clear();
+        return (Py_uhash_t)(uintptr_t)key;
     }
     return (Py_uhash_t)h;
 }