gh-156204: Guard recursion in PyErr_GivenExceptionMatches

Author: BHUVANSH855

Lib/test/test_exceptions.py

@@ -2778,6 +2778,22 @@ def test_except_star_invalid_exception_type(self):
             except (ValueError, 42):
                 pass
 
+    def test_given_exception_matches_deeply_nested_tuple(self):
+        import ctypes
+        lib = ctypes.pythonapi
+        lib.PyErr_GivenExceptionMatches.argtypes = [ctypes.py_object, ctypes.py_object]
+        lib.PyErr_GivenExceptionMatches.restype = ctypes.c_int
+
+        tup = (1, ValueError)
+        for _ in range(50_000):
+            tup = (1, tup)
+
+        # PyErr_GivenExceptionMatches should handle deep recursion safely without SIGSEGV
+        res = lib.PyErr_GivenExceptionMatches(TypeError(), tup)
+        self.assertEqual(res, 0)
+        if lib.PyErr_Occurred():
+            lib.PyErr_Clear()
+
 
 class PEP626Tests(unittest.TestCase):
 

Misc/NEWS.d/next/Core_and_Builtins/2026-08-21-18-49-12.gh-issue-156204.ZusA7e.rst

@@ -0,0 +1,3 @@
+Fix unhandled recursion in :c:func:`PyErr_GivenExceptionMatches` when
+evaluating deeply nested exception tuples, preventing crashes caused by
+stack exhaustion.

Python/errors.c

@@ -335,16 +335,21 @@ PyErr_GivenExceptionMatches(PyObject *err, PyObject *exc)
         return 0;
     }
     if (PyTuple_Check(exc)) {
+        if (Py_EnterRecursiveCall(" in PyErr_GivenExceptionMatches")) {
+            return 0;
+        }
         Py_ssize_t i, n;
-        n = PyTuple_Size(exc);
+        n = PyTuple_GET_SIZE(exc);
         for (i = 0; i < n; i++) {
             /* Test recursively */
-             if (PyErr_GivenExceptionMatches(
-                 err, PyTuple_GET_ITEM(exc, i)))
-             {
-                 return 1;
-             }
+            if (PyErr_GivenExceptionMatches(
+                err, PyTuple_GET_ITEM(exc, i)))
+            {
+                Py_LeaveRecursiveCall();
+                return 1;
+            }
         }
+        Py_LeaveRecursiveCall();
         return 0;
     }
     /* err might be an instance, so check its class. */