gh-135329: prevent infinite traceback loop on Ctrl-C for strace (GH-138133)

Signed-off-by: yihong0618 <zouzou0208@gmail.com>
Co-authored-by: dura0ok <slpmcf@gmail.com>
Co-authored-by: graymon <greyschwinger@gmail.com>
Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>
Co-authored-by: Łukasz Langa <lukasz@langa.pl>

Lib/test/test_pyrepl/eio_test_script.py

@@ -0,0 +1,94 @@
+import errno
+import fcntl
+import os
+import pty
+import signal
+import sys
+import termios
+
+
+def handler(sig, f):
+    pass
+
+
+def create_eio_condition():
+    # SIGINT handler used to produce an EIO.
+    # See https://github.com/python/cpython/issues/135329.
+    try:
+        master_fd, slave_fd = pty.openpty()
+        child_pid = os.fork()
+        if child_pid == 0:
+            try:
+                os.setsid()
+                fcntl.ioctl(slave_fd, termios.TIOCSCTTY, 0)
+                child_process_group_id = os.getpgrp()
+                grandchild_pid = os.fork()
+                if grandchild_pid == 0:
+                    os.setpgid(0, 0)      # set process group for grandchild
+                    os.dup2(slave_fd, 0)  # redirect stdin
+                    if slave_fd > 2:
+                        os.close(slave_fd)
+                    # Fork grandchild for terminal control manipulation
+                    if os.fork() == 0:
+                        sys.exit(0)  # exit the child process that was just obtained
+                    else:
+                        try:
+                            os.tcsetpgrp(0, child_process_group_id)
+                        except OSError:
+                            pass
+                        sys.exit(0)
+                else:
+                    # Back to child
+                    try:
+                        os.setpgid(grandchild_pid, grandchild_pid)
+                    except ProcessLookupError:
+                        pass
+                    os.tcsetpgrp(slave_fd, grandchild_pid)
+                    if slave_fd > 2:
+                        os.close(slave_fd)
+                    os.waitpid(grandchild_pid, 0)
+                    # Manipulate terminal control to create EIO condition
+                    os.tcsetpgrp(master_fd, child_process_group_id)
+                    # Now try to read from master - this might cause EIO
+                    try:
+                        os.read(master_fd, 1)
+                    except OSError as e:
+                        if e.errno == errno.EIO:
+                            print(f"Setup created EIO condition: {e}", file=sys.stderr)
+                    sys.exit(0)
+            except Exception as setup_e:
+                print(f"Setup error: {setup_e}", file=sys.stderr)
+                sys.exit(1)
+        else:
+            # Parent process
+            os.close(slave_fd)
+            os.waitpid(child_pid, 0)
+            # Now replace stdin with master_fd and try to read
+            os.dup2(master_fd, 0)
+            os.close(master_fd)
+            # This should now trigger EIO
+            print(f"Unexpectedly got input: {input()!r}", file=sys.stderr)
+            sys.exit(0)
+    except OSError as e:
+        if e.errno == errno.EIO:
+            print(f"Got EIO: {e}", file=sys.stderr)
+            sys.exit(1)
+        elif e.errno == errno.ENXIO:
+            print(f"Got ENXIO (no such device): {e}", file=sys.stderr)
+            sys.exit(1)  # Treat ENXIO as success too
+        else:
+            print(f"Got other OSError: errno={e.errno} {e}", file=sys.stderr)
+            sys.exit(2)
+    except EOFError as e:
+        print(f"Got EOFError: {e}", file=sys.stderr)
+        sys.exit(3)
+    except Exception as e:
+        print(f"Got unexpected error: {type(e).__name__}: {e}", file=sys.stderr)
+        sys.exit(4)
+
+
+if __name__ == "__main__":
+    # Set up signal handler for coordination
+    signal.signal(signal.SIGUSR1, lambda *a: create_eio_condition())
+    print("READY", flush=True)
+    signal.pause()