gh-62948: IOBase finalizer logs close() errors (#105104)

Doc/whatsnew/3.13.rst

@@ -87,6 +87,15 @@ New Modules
 Improved Modules
 ================
 
+io
+--
+
+The :class:`io.IOBase` finalizer now logs the ``close()`` method errors with
+:data:`sys.unraisablehook`. Previously, errors were ignored silently by default,
+and only logged in :ref:`Python Development Mode <devmode>` or on :ref:`Python
+built on debug mode <debug-build>`.
+(Contributed by Victor Stinner in :gh:`62948`.)
+
 pathlib
 -------
 

Lib/_pyio.py

@@ -33,11 +33,8 @@
 # Rebind for compatibility
 BlockingIOError = BlockingIOError
 
-# Does io.IOBase finalizer log the exception if the close() method fails?
-# The exception is ignored silently by default in release build.
-_IOBASE_EMITS_UNRAISABLE = (hasattr(sys, "gettotalrefcount") or sys.flags.dev_mode)
 # Does open() check its 'errors' argument?
-_CHECK_ERRORS = _IOBASE_EMITS_UNRAISABLE
+_CHECK_ERRORS = (hasattr(sys, "gettotalrefcount") or sys.flags.dev_mode)
 
 
 def text_encoding(encoding, stacklevel=2):
@@ -416,18 +413,9 @@ def __del__(self):
         if closed:
             return
 
-        if _IOBASE_EMITS_UNRAISABLE:
-            self.close()
-        else:
-            # The try/except block is in case this is called at program
-            # exit time, when it's possible that globals have already been
-            # deleted, and then the close() call might fail.  Since
-            # there's nothing we can do about such failures and they annoy
-            # the end users, we suppress the traceback.
-            try:
-                self.close()
-            except:
-                pass
+        # If close() fails, the caller logs the exception with
+        # sys.unraisablehook. close() must be called at the end at __del__().
+        self.close()
 
     ### Inquiries ###
 

Lib/test/test_io.py

@@ -66,10 +66,6 @@ def byteslike(*pos, **kw):
     class EmptyStruct(ctypes.Structure):
         pass
 
-# Does io.IOBase finalizer log the exception if the close() method fails?
-# The exception is ignored silently by default in release build.
-IOBASE_EMITS_UNRAISABLE = (support.Py_DEBUG or sys.flags.dev_mode)
-
 
 def _default_chunk_size():
     """Get the default TextIOWrapper chunk size"""
@@ -1218,10 +1214,7 @@ def test_error_through_destructor(self):
             with self.assertRaises(AttributeError):
                 self.tp(rawio).xyzzy
 
-            if not IOBASE_EMITS_UNRAISABLE:
-                self.assertIsNone(cm.unraisable)
-            elif cm.unraisable is not None:
-                self.assertEqual(cm.unraisable.exc_type, OSError)
+            self.assertEqual(cm.unraisable.exc_type, OSError)
 
     def test_repr(self):
         raw = self.MockRawIO()
@@ -3022,10 +3015,7 @@ def test_error_through_destructor(self):
             with self.assertRaises(AttributeError):
                 self.TextIOWrapper(rawio, encoding="utf-8").xyzzy
 
-            if not IOBASE_EMITS_UNRAISABLE:
-                self.assertIsNone(cm.unraisable)
-            elif cm.unraisable is not None:
-                self.assertEqual(cm.unraisable.exc_type, OSError)
+            self.assertEqual(cm.unraisable.exc_type, OSError)
 
     # Systematic tests of the text I/O API
 

Misc/NEWS.d/next/Library/2023-05-30-18-45-02.gh-issue-62948.1-5wMR.rst

@@ -0,0 +1,4 @@
+The :class:`io.IOBase` finalizer now logs the ``close()`` method errors with
+:data:`sys.unraisablehook`. Previously, errors were ignored silently by default,
+and only logged in :ref:`Python Development Mode <devmode>` or on
+:ref:`Python built on debug mode <debug-build>`.  Patch by Victor Stinner.

Modules/_io/iobase.c

@@ -319,20 +319,8 @@ iobase_finalize(PyObject *self)
         if (PyObject_SetAttr(self, &_Py_ID(_finalizing), Py_True))
             PyErr_Clear();
         res = PyObject_CallMethodNoArgs((PyObject *)self, &_Py_ID(close));
-        /* Silencing I/O errors is bad, but printing spurious tracebacks is
-           equally as bad, and potentially more frequent (because of
-           shutdown issues). */
         if (res == NULL) {
-#ifndef Py_DEBUG
-            if (_Py_GetConfig()->dev_mode) {
-                PyErr_WriteUnraisable(self);
-            }
-            else {
-                PyErr_Clear();
-            }
-#else
             PyErr_WriteUnraisable(self);
-#endif
         }
         else {
             Py_DECREF(res);