gh-135329: prevent infinite traceback loop on Ctrl-C for strace

Lib/_pyrepl/unix_console.py

@@ -336,7 +336,11 @@ def prepare(self):
         raw.lflag |= termios.ISIG
         raw.cc[termios.VMIN] = 1
         raw.cc[termios.VTIME] = 0
-        tcsetattr(self.input_fd, termios.TCSADRAIN, raw)
+        try:
+            tcsetattr(self.input_fd, termios.TCSADRAIN, raw)
+        except termios.error as e:
+            if e.args[0] != errno.EIO:
+                raise
 
         # In macOS terminal we need to deactivate line wrap via ANSI escape code
         if platform.system() == "Darwin" and os.getenv("TERM_PROGRAM") == "Apple_Terminal":
@@ -368,7 +372,14 @@ def restore(self):
         self.__disable_bracketed_paste()
         self.__maybe_write_code(self._rmkx)
         self.flushoutput()
-        tcsetattr(self.input_fd, termios.TCSADRAIN, self.__svtermstate)
+        try:
+            tcsetattr(self.input_fd, termios.TCSADRAIN, self.__svtermstate)
+        except termios.error as e:
+            if e.args[0] != errno.EIO:
+                # gh-135329: when running under external programs (like strace),
+                # tcsetattr may fail with EIO. We can safely ignore this
+                # and continue with default terminal settings.
+                raise
 
         if platform.system() == "Darwin" and os.getenv("TERM_PROGRAM") == "Apple_Terminal":
             os.write(self.output_fd, b"\033[?7h")
@@ -407,6 +418,9 @@ def get_event(self, block: bool = True) -> Event | None:
                             return self.event_queue.get()
                         else:
                             continue
+                    elif err.errno == errno.EIO:
+                        import sys
+                        sys.exit(errno.EIO)
                     else:
                         raise
                 else:

Lib/test/test_pyrepl/test_unix_console.py

@@ -2,11 +2,13 @@
 import os
 import sys
 import unittest
+import errno
+import termios
 from functools import partial
 from test.support import os_helper, force_not_colorized_test_class
 
 from unittest import TestCase
-from unittest.mock import MagicMock, call, patch, ANY
+from unittest.mock import MagicMock, call, patch, ANY, Mock
 
 from .support import handle_all_events, code_to_events
 
@@ -303,3 +305,54 @@ def test_getheightwidth_with_invalid_environ(self, _os_write):
             self.assertIsInstance(console.getheightwidth(), tuple)
             os.environ = []
             self.assertIsInstance(console.getheightwidth(), tuple)
+
+
+class TestUnixConsoleEIOHandling(TestCase):
+
+    @patch('_pyrepl.unix_console.tcsetattr')
+    @patch('_pyrepl.unix_console.tcgetattr')
+    def test_eio_error_handling_in_prepare(self, mock_tcgetattr, mock_tcsetattr):
+        mock_termios = Mock()
+        mock_termios.iflag = 0
+        mock_termios.oflag = 0
+        mock_termios.cflag = 0
+        mock_termios.lflag = 0
+        mock_termios.cc = [0] * 32
+        mock_termios.copy.return_value = mock_termios
+        mock_tcgetattr.return_value = mock_termios
+
+        mock_tcsetattr.side_effect = termios.error(errno.EIO, "Input/output error")
+
+        console = UnixConsole(term="xterm")
+
+        try:
+            console.prepare()
+        except termios.error as e:
+            if e.args[0] == errno.EIO:
+                self.fail("EIO error should have been handled gracefully in prepare()")
+            raise
+
+    @patch('_pyrepl.unix_console.tcsetattr')
+    @patch('_pyrepl.unix_console.tcgetattr')
+    def test_eio_error_handling_in_restore(self, mock_tcgetattr, mock_tcsetattr):
+
+        mock_termios = Mock()
+        mock_termios.iflag = 0
+        mock_termios.oflag = 0
+        mock_termios.cflag = 0
+        mock_termios.lflag = 0
+        mock_termios.cc = [0] * 32
+        mock_termios.copy.return_value = mock_termios
+        mock_tcgetattr.return_value = mock_termios
+
+        console = UnixConsole(term="xterm")
+        console.prepare()
+
+        mock_tcsetattr.side_effect = termios.error(errno.EIO, "Input/output error")
+
+        try:
+            console.restore()
+        except termios.error as e:
+            if e.args[0] == errno.EIO:
+                self.fail("EIO error should have been handled gracefully in restore()")
+            raise

Misc/NEWS.d/next/Library/2025-08-25-18-06-04.gh-issue-138133.Zh9rGo.rst

@@ -0,0 +1 @@
+Prevent infinite traceback loop when sending CTRL^C to Python through ``strace``.