pdb.py

"""
The Python Debugger Pdb
=======================

To use the debugger in its simplest form:

 >>> import pdb
 >>> pdb.run('<a statement>')

The debugger's prompt is '(Pdb) '. This will stop in the first
function call in <a statement>.

Alternatively, if a statement terminated with an unhandled exception,
you can use pdb's post-mortem facility to inspect the contents of the
traceback:

 >>> <a statement>
 <exception traceback>
 >>> import pdb
 >>> pdb.pm()

The commands recognized by the debugger are listed in the next
section. Most can be abbreviated as indicated; e.g., h(elp) means
that 'help' can be typed as 'h' or 'help' (but not as 'he' or 'hel',
nor as 'H' or 'Help' or 'HELP'). Optional arguments are enclosed in
square brackets. Alternatives in the command syntax are separated
by a vertical bar (|).

A blank line repeats the previous command literally, except for
'list', where it lists the next 11 lines.

Commands that the debugger doesn't recognize are assumed to be Python
statements and are executed in the context of the program being
debugged. Python statements can also be prefixed with an exclamation
point ('!'). This is a powerful way to inspect the program being
debugged; it is even possible to change variables or call functions.
When an exception occurs in such a statement, the exception name is
printed but the debugger's state is not changed.

The debugger supports aliases, which can save typing. And aliases can
have parameters (see the alias help entry) which allows one a certain
level of adaptability to the context under examination.

Multiple commands may be entered on a single line, separated by the
pair ';;'. No intelligence is applied to separating the commands; the
input is split at the first ';;', even if it is in the middle of a
quoted string.

If a file ".pdbrc" exists in your home directory or in the current
directory, it is read in and executed as if it had been typed at the
debugger prompt. This is particularly useful for aliases. If both
files exist, the one in the home directory is read first and aliases
defined there can be overridden by the local file. This behavior can be
disabled by passing the "readrc=False" argument to the Pdb constructor.

Aside from aliases, the debugger is not directly programmable; but it
is implemented as a class from which you can derive your own debugger
class, which you can make as fancy as you like.


Debugger commands
=================

"""
# NOTE: the actual command documentation is collected from docstrings of the
# commands and is appended to __doc__ after the class has been defined.

import os
import io
import re
import sys
import cmd
import bdb
import dis
import code
import glob
import json
import stat
import token
import types
import atexit
import codeop
import pprint
import signal
import socket
import typing
import asyncio
import inspect
import weakref
import builtins
import tempfile
import textwrap
import tokenize
import itertools
import traceback
import linecache
import selectors
import threading
import _colorize

from contextlib import ExitStack, closing, contextmanager
from types import CodeType
from warnings import deprecated

try:
 import _pyrepl.utils
except ModuleNotFoundError:
 _pyrepl = None


class Restart(Exception):
 """Causes a debugger to be restarted for the debugged python program."""
 pass

__all__ = ["run", "pm", "Pdb", "runeval", "runctx", "runcall", "set_trace",
 "post_mortem", "set_default_backend", "get_default_backend", "help"]


def find_first_executable_line(code):
 """ Try to find the first executable line of the code object.

 Equivalently, find the line number of the instruction that's
 after RESUME

 Return code.co_firstlineno if no executable line is found.
 """
 prev = None
 for instr in dis.get_instructions(code):
 if prev is not None and prev.opname == 'RESUME':
 if instr.positions.lineno is not None:
 return instr.positions.lineno
 return code.co_firstlineno
 prev = instr
 return code.co_firstlineno

def find_function(funcname, filename):
 cre = re.compile(r'(?:async\s+)?def\s+%s(\s*\[.+\])?\s*[(]' % re.escape(funcname))
 try:
 fp = tokenize.open(filename)
 except OSError:
 lines = linecache.getlines(filename)
 if not lines:
 return None
 fp = io.StringIO(''.join(lines))
 funcdef = ""
 funcstart = 0
 # consumer of this info expects the first line to be 1
 with fp:
 for lineno, line in enumerate(fp, start=1):
 if cre.match(line):
 funcstart, funcdef = lineno, line
 elif funcdef:
 funcdef += line

 if funcdef:
 try:
 code = compile(funcdef, filename, 'exec')
 except SyntaxError:
 continue
 # We should always be able to find the code object here
 funccode = next(c for c in code.co_consts if
 isinstance(c, CodeType) and c.co_name == funcname)
 lineno_offset = find_first_executable_line(funccode)
 return funcname, filename, funcstart + lineno_offset - 1
 return None

def lasti2lineno(code, lasti):
 linestarts = list(dis.findlinestarts(code))
 linestarts.reverse()
 for i, lineno in linestarts:
 if lasti >= i:
 return lineno
 return 0


class _rstr(str):
 """String that doesn't quote its repr."""
 def __repr__(self):
 return self


class _ExecutableTarget:
 filename: str
 code: CodeType | str
 namespace: dict


class _ScriptTarget(_ExecutableTarget):
 def __init__(self, target):
 self._check(target)
 self._target = self._safe_realpath(target)

 # If PYTHONSAFEPATH (-P) is not set, sys.path[0] is the directory
 # of pdb, and we should replace it with the directory of the script
 if not sys.flags.safe_path:
 sys.path[0] = os.path.dirname(self._target)

 @staticmethod
 def _check(target):
 """
 Check that target is plausibly a script.
 """
 if not os.path.exists(target):
 print(f'Error: {target} does not exist')
 sys.exit(1)
 if os.path.isdir(target):
 print(f'Error: {target} is a directory')
 sys.exit(1)

 @staticmethod
 def _safe_realpath(path):
 """
 Return the canonical path (realpath) if it is accessible from the userspace.
 Otherwise (for example, if the path is a symlink to an anonymous pipe),
 return the original path.

 See GH-142315.
 """
 realpath = os.path.realpath(path)
 return realpath if os.path.exists(realpath) else path

 def __repr__(self):
 return self._target

 @property
 def filename(self):
 return self._target

 @property
 def code(self):
 # Open the file each time because the file may be modified
 with io.open_code(self._target) as fp:
 return f"exec(compile({fp.read()!r}, {self._target!r}, 'exec'))"

 @property
 def namespace(self):
 return dict(
 __name__='__main__',
 __file__=self._target,
 __builtins__=__builtins__,
 __spec__=None,
 )


class _ModuleTarget(_ExecutableTarget):
 def __init__(self, target):
 self._target = target

 import runpy
 try:
 _, self._spec, self._code = runpy._get_module_details(self._target)
 except ImportError as e:
 print(f"ImportError: {e}")
 sys.exit(1)
 except Exception:
 traceback.print_exc()
 sys.exit(1)

 def __repr__(self):
 return self._target

 @property
 def filename(self):
 return self._code.co_filename

 @property
 def code(self):
 return self._code

 @property
 def namespace(self):
 return dict(
 __name__='__main__',
 __file__=os.path.normcase(os.path.abspath(self.filename)),
 __package__=self._spec.parent,
 __loader__=self._spec.loader,
 __spec__=self._spec,
 __builtins__=__builtins__,
 )


class _ZipTarget(_ExecutableTarget):
 def __init__(self, target):
 import runpy

 self._target = os.path.realpath(target)
 sys.path.insert(0, self._target)
 try:
 _, self._spec, self._code = runpy._get_main_module_details()
 except ImportError as e:
 print(f"ImportError: {e}")
 sys.exit(1)
 except Exception:
 traceback.print_exc()
 sys.exit(1)

 def __repr__(self):
 return self._target

 @property
 def filename(self):
 return self._code.co_filename

 @property
 def code(self):
 return self._code

 @property
 def namespace(self):
 return dict(
 __name__='__main__',
 __file__=os.path.normcase(os.path.abspath(self.filename)),
 __package__=self._spec.parent,
 __loader__=self._spec.loader,
 __spec__=self._spec,
 __builtins__=__builtins__,
 )


class _PdbInteractiveConsole(code.InteractiveConsole):
 def __init__(self, ns=None, message=None):
 self._message = message
 super().__init__(locals=ns, local_exit=True)

 def write(self, data):
 if self._message is not None:
 self._message(data, end='')
 else:
 super().write(data)

 def more_lines(self, text):
 # Generic Python multi-line completeness heuristic.
 # Strips pyrepl's trailing auto-indent before compiling.
 # This should be functionally identical to simple_interact._more_lines
 src = text.rstrip(" \t")
 n = len(src)
 if n > 0 and text[n-1] == '\n':
 text = src
 try:
 code_obj = self.compile(text, "<stdin>", "single")
 except (OverflowError, SyntaxError, ValueError):
 lines = text.splitlines(keepends=True)
 if len(lines) == 1:
 return False
 last = lines[-1]
 return ((last.startswith((" ", "\t")) or last.strip() != "")
 and not last.endswith("\n"))
 return code_obj is None


# Interaction prompt line will separate file and call info from code
# text using value of line_prefix string. A newline and arrow may
# be to your liking. You can set it once pdb is imported using the
# command "pdb.line_prefix = '\n% '".
# line_prefix = ': ' # Use this to get the old situation back
line_prefix = '\n-> ' # Probably a better default


# The default backend to use for Pdb instances if not specified
# Should be either 'settrace' or 'monitoring'
_default_backend = 'settrace'


def set_default_backend(backend):
 """Set the default backend to use for Pdb instances."""
 global _default_backend
 if backend not in ('settrace', 'monitoring'):
 raise ValueError("Invalid backend: %s" % backend)
 _default_backend = backend


def get_default_backend():
 """Get the default backend to use for Pdb instances."""
 return _default_backend


def _pyrepl_available():
 """return whether pdb should use _pyrepl for input"""
 if os.getenv("PYTHON_BASIC_REPL"):
 CAN_USE_PYREPL = False
 else:
 try:
 from _pyrepl.main import CAN_USE_PYREPL
 except ModuleNotFoundError:
 CAN_USE_PYREPL = False
 return CAN_USE_PYREPL


class PdbPyReplInput:
 def __init__(self, pdb_instance, stdin, stdout, prompt):
 import _pyrepl.readline

 self.pdb_instance = pdb_instance
 self.prompt = prompt
 self.console = _PdbInteractiveConsole()
 if not (os.isatty(stdin.fileno())):
 raise ValueError("stdin is not a TTY")
 self.readline_wrapper = _pyrepl.readline._ReadlineWrapper(
 f_in=stdin.fileno(),
 f_out=stdout.fileno(),
 config=_pyrepl.readline.ReadlineConfig(
 completer_delims=frozenset(' \t\n`@#%^&*()=+[{]}\\|;:\'",<>?')
 )
 )
 self.readline_wrapper.get_reader().gen_colors = self.gen_colors

 def readline(self):

 def more_lines(text):
 if text.strip() == "\x1a":
 # Ctrl + Z raises EOFError to quit pdb
 # This is similarly handled in simple_interact.py
 raise EOFError
 cmd, _, line = self.pdb_instance.parseline(text)
 if not line or not cmd:
 return False
 func = getattr(self.pdb_instance, 'do_' + cmd, None)
 if func is not None:
 return False
 return self.console.more_lines(text)

 try:
 pyrepl_completer = self.readline_wrapper.get_completer()
 self.readline_wrapper.set_completer(self.complete)
 multiline = (
 self.readline_wrapper.multiline_input(
 more_lines,
 self.prompt,
 '... ' + ' ' * (len(self.prompt) - 4)
 ) + '\n'
 )
 return multiline
 except EOFError:
 return 'EOF'
 finally:
 self.readline_wrapper.set_completer(pyrepl_completer)

 def complete(self, text, state):
 """
 This function is very similar to cmd.Cmd.complete.
 However, cmd.Cmd.complete assumes that we use readline module, but
 pyrepl does not use it.
 """
 if state == 0:
 origline = self.readline_wrapper.get_line_buffer()
 line = origline.lstrip()
 stripped = len(origline) - len(line)
 begidx = self.readline_wrapper.get_begidx() - stripped
 endidx = self.readline_wrapper.get_endidx() - stripped
 if begidx > 0:
 cmd, args, foo = self.pdb_instance.parseline(line)
 if not cmd:
 compfunc = self.pdb_instance.completedefault
 else:
 try:
 compfunc = getattr(self.pdb_instance, 'complete_' + cmd)
 except AttributeError:
 compfunc = self.pdb_instance.completedefault
 else:
 compfunc = self.pdb_instance.completenames
 self.completion_matches = compfunc(text, line, begidx, endidx)
 try:
 return self.completion_matches[state]
 except IndexError:
 return None

 def gen_colors(self, buffer):
 from _pyrepl.utils import ColorSpan, Span

 if not buffer.strip():
 return

 leading_spaces = len(buffer) - len(buffer.lstrip())
 leading_text = buffer.split()[0]
 if hasattr(self.pdb_instance, 'do_' + leading_text):
 yield ColorSpan(
 Span(leading_spaces, leading_spaces + len(leading_text) - 1),
 "soft_keyword"
 )
 # Redact the command text with spaces so there will be no duplicated
 # color span generated for it later.
 redact_length = leading_spaces + len(leading_text)
 buffer = ' ' * redact_length + buffer[redact_length:]

 yield from _pyrepl.utils.gen_colors(buffer)


class Pdb(bdb.Bdb, cmd.Cmd):
 _previous_sigint_handler = None

 # Limit the maximum depth of chained exceptions, we should be handling cycles,
 # but in case there are recursions, we stop at 999.
 MAX_CHAINED_EXCEPTION_DEPTH = 999

 _file_mtime_table = {}

 _last_pdb_instance = None

 def __init__(self, completekey='tab', stdin=None, stdout=None, skip=None,
 nosigint=False, readrc=True, mode=None, backend=None, colorize=False):
 bdb.Bdb.__init__(self, skip=skip, backend=backend if backend else get_default_backend())
 cmd.Cmd.__init__(self, completekey, stdin, stdout)
 sys.audit("pdb.Pdb")
 if stdin is not None and stdin is not sys.stdin:
 self.use_rawinput = False
 self.prompt = '(Pdb) '
 self.aliases = {}
 self.displaying = {}
 self.mainpyfile = ''
 self._wait_for_mainpyfile = False
 self.tb_lineno = {}
 self.mode = mode
 self.colorize = colorize and _colorize.can_colorize(file=stdout or sys.stdout)
 # Try to load readline if it exists
 try:
 import readline
 # remove some common file name delimiters
 readline.set_completer_delims(' \t\n`@#%^&*()=+[{]}\\|;:\'",<>?')
 except ImportError:
 pass

 self.pyrepl_input = None
 if _pyrepl_available():
 try:
 self.pyrepl_input = PdbPyReplInput(self, self.stdin, self.stdout, self.prompt)
 except Exception:
 pass
 self.allow_kbdint = False
 self.nosigint = nosigint
 # Consider these characters as part of the command so when the users type
 # c.a or c['a'], it won't be recognized as a c(ontinue) command
 self.identchars = cmd.Cmd.identchars + '=.[](),"\'+-*/%@&|<>~^'

 # Read ~/.pdbrc and ./.pdbrc
 self.rcLines = []
 if readrc:
 home_rcfile = os.path.expanduser("~/.pdbrc")
 local_rcfile = os.path.abspath(".pdbrc")

 try:
 with open(home_rcfile, encoding='utf-8') as rcfile:
 self.rcLines.extend(rcfile)
 except OSError:
 pass

 if local_rcfile != home_rcfile:
 try:
 with open(local_rcfile, encoding='utf-8') as rcfile:
 self.rcLines.extend(rcfile)
 except OSError:
 pass

 self.commands = {} # associates a command list to breakpoint numbers
 self.commands_defining = False # True while in the process of defining
 # a command list
 self.commands_bnum = None # The breakpoint number for which we are
 # defining a list

 self.async_shim_frame = None
 self.async_awaitable = None

 self._chained_exceptions = tuple()
 self._chained_exception_index = 0

 self._current_task = None

 self.lineno = None
 self.stack = []
 self.curindex = 0
 self.curframe = None
 self._user_requested_quit = False

 def set_trace(self, frame=None, *, commands=None):
 Pdb._last_pdb_instance = self
 if frame is None:
 frame = sys._getframe().f_back

 if commands is not None:
 self.rcLines.extend(commands)

 super().set_trace(frame)

 async def set_trace_async(self, frame=None, *, commands=None):
 if self.async_awaitable is not None:
 # We are already in a set_trace_async call, do not mess with it
 return

 if frame is None:
 frame = sys._getframe().f_back

 # We need set_trace to set up the basics, however, this will call
 # set_stepinstr() will we need to compensate for, because we don't
 # want to trigger on calls
 self.set_trace(frame, commands=commands)
 # Changing the stopframe will disable trace dispatch on calls
 self.stopframe = frame
 # We need to stop tracing because we don't have the privilege to avoid
 # triggering tracing functions as normal, as we are not already in
 # tracing functions
 self.stop_trace()

 self.async_shim_frame = sys._getframe()
 self.async_awaitable = None

 while True:
 self.async_awaitable = None
 # Simulate a trace event
 # This should bring up pdb and make pdb believe it's debugging the
 # caller frame
 self.trace_dispatch(frame, "opcode", None)
 if self.async_awaitable is not None:
 try:
 if self.breaks:
 with self.set_enterframe(frame):
 # set_continue requires enterframe to work
 self.set_continue()
 self.start_trace()
 await self.async_awaitable
 except Exception:
 self._error_exc()
 else:
 break

 self.async_shim_frame = None

 # start the trace (the actual command is already set by set_* calls)
 if self.returnframe is None and self.stoplineno == -1 and not self.breaks:
 # This means we did a continue without any breakpoints, we should not
 # start the trace
 return

 self.start_trace()

 def sigint_handler(self, signum, frame):
 if self.allow_kbdint:
 raise KeyboardInterrupt
 self.message("\nProgram interrupted. (Use 'cont' to resume).")
 self.set_step()
 self.set_trace(frame)

 def reset(self):
 bdb.Bdb.reset(self)
 self.forget()

 def forget(self):
 self.lineno = None
 self.stack = []
 self.curindex = 0
 if self.curframe:
 self.curframe.f_globals.pop('__pdb_convenience_variables', None)
 self.curframe = None
 self.tb_lineno.clear()

 def setup(self, f, tb):
 self.forget()
 self.stack, self.curindex = self.get_stack(f, tb)
 while tb:
 # when setting up post-mortem debugging with a traceback, save all
 # the original line numbers to be displayed along the current line
 # numbers (which can be different, e.g. due to finally clauses)
 lineno = lasti2lineno(tb.tb_frame.f_code, tb.tb_lasti)
 self.tb_lineno[tb.tb_frame] = lineno
 tb = tb.tb_next
 self.curframe = self.stack[self.curindex][0]
 self.set_convenience_variable(self.curframe, '_frame', self.curframe)
 if self._current_task:
 self.set_convenience_variable(self.curframe, '_asynctask', self._current_task)
 self._save_initial_file_mtime(self.curframe)

 if self._chained_exceptions:
 self.set_convenience_variable(
 self.curframe,
 '_exception',
 self._chained_exceptions[self._chained_exception_index],
 )

 if self.rcLines:
 self.cmdqueue = [
 line for line in self.rcLines
 if line.strip() and not line.strip().startswith("#")
 ]
 self.rcLines = []

 @property
 @deprecated("The frame locals reference is no longer cached. Use 'curframe.f_locals' instead.")
 def curframe_locals(self):
 return self.curframe.f_locals

 @curframe_locals.setter
 @deprecated("Setting 'curframe_locals' no longer has any effect. Update the contents of 'curframe.f_locals' instead.")
 def curframe_locals(self, value):
 pass

 # Override Bdb methods

 def user_call(self, frame, argument_list):
 """This method is called when there is the remote possibility
 that we ever need to stop in this function."""
 if self._wait_for_mainpyfile:
 return
 if self.stop_here(frame):
 self.message('--Call--')
 self.interaction(frame, None)

 def user_line(self, frame):
 """This function is called when we stop or break at this line."""
 if self._wait_for_mainpyfile:
 if (self.mainpyfile != self.canonic(frame.f_code.co_filename)):
 return
 self._wait_for_mainpyfile = False
 if self.trace_opcodes:
 # GH-127321
 # We want to avoid stopping at an opcode that does not have
 # an associated line number because pdb does not like it
 if frame.f_lineno is None:
 self.set_stepinstr()
 return
 self.bp_commands(frame)
 self.interaction(frame, None)

 user_opcode = user_line

 def bp_commands(self, frame):
 """Call every command that was set for the current active breakpoint
 (if there is one).

 Returns True if the normal interaction function must be called,
 False otherwise."""
 # self.currentbp is set in bdb in Bdb.break_here if a breakpoint was hit
 if getattr(self, "currentbp", False) and \
 self.currentbp in self.commands:
 currentbp = self.currentbp
 self.currentbp = 0
 for line in self.commands[currentbp]:
 self.cmdqueue.append(line)
 self.cmdqueue.append(f'_pdbcmd_restore_lastcmd {self.lastcmd}')

 def user_return(self, frame, return_value):
 """This function is called when a return trap is set here."""
 if self._wait_for_mainpyfile:
 return
 frame.f_locals['__return__'] = return_value
 self.set_convenience_variable(frame, '_retval', return_value)
 self.message('--Return--')
 self.interaction(frame, None)

 def user_exception(self, frame, exc_info):
 """This function is called if an exception occurs,
 but only if we are to stop at or just below this level."""
 if self._wait_for_mainpyfile:
 return
 exc_type, exc_value, exc_traceback = exc_info
 frame.f_locals['__exception__'] = exc_type, exc_value
 self.set_convenience_variable(frame, '_exception', exc_value)

 # An 'Internal StopIteration' exception is an exception debug event
 # issued by the interpreter when handling a subgenerator run with
 # 'yield from' or a generator controlled by a for loop. No exception has
 # actually occurred in this case. The debugger uses this debug event to
 # stop when the debuggee is returning from such generators.
 prefix = 'Internal ' if (not exc_traceback
 and exc_type is StopIteration) else ''
 self.message('%s%s' % (prefix, self._format_exc(exc_value)))
 self.interaction(frame, exc_traceback)

 @contextmanager
 def _replace_attribute(self, attrs):
 original_attrs = {}
 for attr, value in attrs.items():
 original_attrs[attr] = getattr(self, attr)
 setattr(self, attr, value)
 try:
 yield
 finally:
 for attr, value in original_attrs.items():
 setattr(self, attr, value)

 @contextmanager
 def _maybe_use_pyrepl_as_stdin(self):
 if self.pyrepl_input is None:
 yield
 return

 with self._replace_attribute({
 'stdin': self.pyrepl_input,
 'use_rawinput': False,
 'prompt': '',
 }):
 yield

 # General interaction function
 def _cmdloop(self):
 while True:
 try:
 # keyboard interrupts allow for an easy way to cancel
 # the current command, so allow them during interactive input
 self.allow_kbdint = True
 with self._maybe_use_pyrepl_as_stdin():
 self.cmdloop()
 self.allow_kbdint = False
 break
 except KeyboardInterrupt:
 self.message('--KeyboardInterrupt--')

 def _save_initial_file_mtime(self, frame):
 """save the mtime of the all the files in the frame stack in the file mtime table
 if they haven't been saved yet."""
 while frame:
 filename = frame.f_code.co_filename
 if filename not in self._file_mtime_table:
 try:
 self._file_mtime_table[filename] = os.path.getmtime(filename)
 except Exception:
 pass
 frame = frame.f_back

 def _validate_file_mtime(self):
 """Check if the source file of the current frame has been modified.
 If so, give a warning and reset the modify time to current."""
 try:
 filename = self.curframe.f_code.co_filename
 mtime = os.path.getmtime(filename)
 except Exception:
 return
 if (filename in self._file_mtime_table and
 mtime != self._file_mtime_table[filename]):
 self.message(f"*** WARNING: file '{filename}' was edited, "
 "running stale code until the program is rerun")
 self._file_mtime_table[filename] = mtime

 # Called before loop, handles display expressions
 # Set up convenience variable containers
 def _show_display(self):
 displaying = self.displaying.get(self.curframe)
 if displaying:
 for expr, oldvalue in displaying.items():
 newvalue = self._getval_except(expr)
 # check for identity first; this prevents custom __eq__ to
 # be called at every loop, and also prevents instances whose
 # fields are changed to be displayed
 if newvalue is not oldvalue and newvalue != oldvalue:
 displaying[expr] = newvalue
 self.message('display %s: %s [old: %s]' %
 (expr, self._safe_repr(newvalue, expr),
 self._safe_repr(oldvalue, expr)))

 def _get_tb_and_exceptions(self, tb_or_exc):
 """
 Given a traceback or an exception, return a tuple of chained exceptions
 and current traceback to inspect.

 This will deal with selecting the right ``__cause__`` or ``__context__``
 as well as handling cycles, and return a flattened list of exceptions we
 can jump to with do_exceptions.

 """
 _exceptions = []
 if isinstance(tb_or_exc, BaseException):
 traceback, current = tb_or_exc.__traceback__, tb_or_exc

 while current is not None:
 if current in _exceptions:
 break
 _exceptions.append(current)
 if current.__cause__ is not None:
 current = current.__cause__
 elif (
 current.__context__ is not None and not current.__suppress_context__
 ):
 current = current.__context__

 if len(_exceptions) >= self.MAX_CHAINED_EXCEPTION_DEPTH:
 self.message(
 f"More than {self.MAX_CHAINED_EXCEPTION_DEPTH}"
 " chained exceptions found, not all exceptions"
 "will be browsable with `exceptions`."
 )
 break
 else:
 traceback = tb_or_exc
 return tuple(reversed(_exceptions)), traceback

 @contextmanager
 def _hold_exceptions(self, exceptions):
 """
 Context manager to ensure proper cleaning of exceptions references

 When given a chained exception instead of a traceback,
 pdb may hold references to many objects which may leak memory.

 We use this context manager to make sure everything is properly cleaned

 """
 try:
 self._chained_exceptions = exceptions
 self._chained_exception_index = len(exceptions) - 1
 yield
 finally:
 # we can't put those in forget as otherwise they would
 # be cleared on exception change
 self._chained_exceptions = tuple()
 self._chained_exception_index = 0

 def _get_asyncio_task(self):
 try:
 task = asyncio.current_task()
 except RuntimeError:
 task = None
 return task

 def interaction(self, frame, tb_or_exc):
 # Restore the previous signal handler at the Pdb prompt.
 if Pdb._previous_sigint_handler:
 try:
 signal.signal(signal.SIGINT, Pdb._previous_sigint_handler)
 except ValueError: # ValueError: signal only works in main thread
 pass
 else:
 Pdb._previous_sigint_handler = None

 self._current_task = self._get_asyncio_task()

 _chained_exceptions, tb = self._get_tb_and_exceptions(tb_or_exc)
 if isinstance(tb_or_exc, BaseException):
 assert tb is not None, "main exception must have a traceback"
 with self._hold_exceptions(_chained_exceptions):
 self.setup(frame, tb)
 # We should print the stack entry if and only if the user input
 # is expected, and we should print it right before the user input.
 # We achieve this by appending _pdbcmd_print_frame_status to the
 # command queue. If cmdqueue is not exhausted, the user input is
 # not expected and we will not print the stack entry.
 self.cmdqueue.append('_pdbcmd_print_frame_status')
 self._cmdloop()
 # If _pdbcmd_print_frame_status is not used, pop it out
 if self.cmdqueue and self.cmdqueue[-1] == '_pdbcmd_print_frame_status':
 self.cmdqueue.pop()
 self.forget()

 def displayhook(self, obj):
 """Custom displayhook for the exec in default(), which prevents
 assignment of the _ variable in the builtins.
 """
 # reproduce the behavior of the standard displayhook, not printing None
 if obj is not None:
 self.message(repr(obj))

 @contextmanager
 def _enable_multiline_input(self):
 try:
 import readline
 except ImportError:
 yield
 return

 def input_auto_indent():
 last_index = readline.get_current_history_length()
 last_line = readline.get_history_item(last_index)
 if last_line:
 if last_line.isspace():
 # If the last line is empty, we don't need to indent
 return

 last_line = last_line.rstrip('\r\n')
 indent = len(last_line) - len(last_line.lstrip())
 if last_line.endswith(":"):
 indent += 4
 readline.insert_text(' ' * indent)

 completenames = self.completenames
 try:
 self.completenames = self.complete_multiline_names
 readline.set_startup_hook(input_auto_indent)
 yield
 finally:
 readline.set_startup_hook()
 self.completenames = completenames
 return

 def _exec_in_closure(self, source, globals, locals):
 """ Run source code in closure so code object created within source
 can find variables in locals correctly

 returns True if the source is executed, False otherwise
 """

 # Determine if the source should be executed in closure. Only when the
 # source compiled to multiple code objects, we should use this feature.
 # Otherwise, we can just raise an exception and normal exec will be used.

 code = compile(source, "<string>", "exec")
 if not any(isinstance(const, CodeType) for const in code.co_consts):
 return False

 # locals could be a proxy which does not support pop
 # copy it first to avoid modifying the original locals
 locals_copy = dict(locals)

 locals_copy["__pdb_eval__"] = {
 "result": None,
 "write_back": {}
 }

 # If the source is an expression, we need to print its value
 try:
 compile(source, "<string>", "eval")
 except SyntaxError:
 pass
 else:
 source = "__pdb_eval__['result'] = " + source

 # Add write-back to update the locals
 source = ("try:\n" +
 textwrap.indent(source, " ") + "\n" +
 "finally:\n" +
 " __pdb_eval__['write_back'] = locals()")

 # Build a closure source code with freevars from locals like:
 # def __pdb_outer():
 # var = None
 # def __pdb_scope(): # This is the code object we want to execute
 # nonlocal var
 # <source>
 # return __pdb_scope.__code__
 source_with_closure = ("def __pdb_outer():\n" +
 "\n".join(f" {var} = None" for var in locals_copy) + "\n" +
 " def __pdb_scope():\n" +
 "\n".join(f" nonlocal {var}" for var in locals_copy) + "\n" +
 textwrap.indent(source, " ") + "\n" +
 " return __pdb_scope.__code__"
 )

 # Get the code object of __pdb_scope()
 # The exec fills locals_copy with the __pdb_outer() function and we can call
 # that to get the code object of __pdb_scope()
 ns = {}
 try:
 exec(source_with_closure, {}, ns)
 except Exception:
 return False
 code = ns["__pdb_outer"]()

 cells = tuple(types.CellType(locals_copy.get(var)) for var in code.co_freevars)

 try:
 exec(code, globals, locals_copy, closure=cells)
 except Exception:
 return False

 # get the data we need from the statement
 pdb_eval = locals_copy["__pdb_eval__"]

 # __pdb_eval__ should not be updated back to locals
 pdb_eval["write_back"].pop("__pdb_eval__")

 # Write all local variables back to locals
 locals.update(pdb_eval["write_back"])
 eval_result = pdb_eval["result"]
 if eval_result is not None:
 self.message(repr(eval_result))

 return True

 def _exec_await(self, source, globals, locals):
 """ Run source code that contains await by playing with async shim frame"""
 # Put the source in an async function
 source_async = (
 "async def __pdb_await():\n" +
 textwrap.indent(source, " ") + '\n' +
 " __pdb_locals.update(locals())"
 )
 ns = globals | locals
 # We use __pdb_locals to do write back
 ns["__pdb_locals"] = locals
 exec(source_async, ns)
 self.async_awaitable = ns["__pdb_await"]()

 def _read_code(self, line):
 buffer = line
 is_await_code = False
 code = None
 try:
 if (code := codeop.compile_command(line + '\n', '<stdin>', 'single')) is None:
 # Multi-line mode
 with self._enable_multiline_input():
 buffer = line
 continue_prompt = "... "
 while (code := codeop.compile_command(buffer, '<stdin>', 'single')) is None:
 if self.use_rawinput:
 try:
 line = input(continue_prompt)
 except (EOFError, KeyboardInterrupt):
 self.lastcmd = ""
 print('\n')
 return None, None, False
 else:
 self.stdout.write(continue_prompt)
 self.stdout.flush()
 line = self.stdin.readline()
 if not len(line):
 self.lastcmd = ""
 self.stdout.write('\n')
 self.stdout.flush()
 return None, None, False
 else:
 line = line.rstrip('\r\n')
 if line.isspace():
 # empty line, just continue
 buffer += '\n'
 else:
 buffer += '\n' + line
 self.lastcmd = buffer
 except SyntaxError as e:
 # Maybe it's an await expression/statement
 if (
 self.async_shim_frame is not None
 and e.msg == "'await' outside function"
 ):
 is_await_code = True
 else:
 raise

 return code, buffer, is_await_code

 def default(self, line):
 if line[:1] == '!': line = line[1:].strip()
 locals = self.curframe.f_locals
 globals = self.curframe.f_globals
 try:
 code, buffer, is_await_code = self._read_code(line)
 if buffer is None:
 return
 save_stdout = sys.stdout
 save_stdin = sys.stdin
 save_displayhook = sys.displayhook
 try:
 sys.stdin = self.stdin
 sys.stdout = self.stdout
 sys.displayhook = self.displayhook
 if is_await_code:
 self._exec_await(buffer, globals, locals)
 return True
 else:
 if not self._exec_in_closure(buffer, globals, locals):
 exec(code, globals, locals)
 finally:
 sys.stdout = save_stdout
 sys.stdin = save_stdin
 sys.displayhook = save_displayhook
 except:
 self._error_exc()

 def _replace_convenience_variables(self, line):
 """Replace the convenience variables in 'line' with their values.
 e.g. $foo is replaced by __pdb_convenience_variables["foo"].
 Note: such pattern in string literals will be skipped"""

 if "$" not in line:
 return line

 dollar_start = dollar_end = (-1, -1)
 replace_variables = []
 try:
 for t in tokenize.generate_tokens(io.StringIO(line).readline):
 token_type, token_string, start, end, _ = t
 if token_type == token.OP and token_string == '$':
 dollar_start, dollar_end = start, end
 elif start == dollar_end and token_type == token.NAME:
 # line is a one-line command so we only care about column
 replace_variables.append((dollar_start[1], end[1], token_string))
 except tokenize.TokenError:
 return line

 if not replace_variables:
 return line

 last_end = 0
 line_pieces = []
 for start, end, name in replace_variables:
 line_pieces.append(line[last_end:start] + f'__pdb_convenience_variables["{name}"]')
 last_end = end
 line_pieces.append(line[last_end:])

 return ''.join(line_pieces)

 def precmd(self, line):
 """Handle alias expansion and ';;' separator."""
 if not line.strip():
 return line
 args = line.split()
 while args[0] in self.aliases:
 line = self.aliases[args[0]]
 for idx in range(1, 10):
 if f'%{idx}' in line:
 if idx >= len(args):
 self.error(f"Not enough arguments for alias '{args[0]}'")
 # This is a no-op
 return "!"
 line = line.replace(f'%{idx}', args[idx])
 elif '%*' not in line:
 if idx < len(args):
 self.error(f"Too many arguments for alias '{args[0]}'")
 # This is a no-op
 return "!"
 break

 line = line.replace("%*", ' '.join(args[1:]))
 args = line.split()
 # split into ';;' separated commands
 # unless it's an alias command
 if args[0] != 'alias':
 marker = line.find(';;')
 if marker >= 0:
 # queue up everything after marker
 next = line[marker+2:].lstrip()
 self.cmdqueue.insert(0, next)
 line = line[:marker].rstrip()

 # Replace all the convenience variables
 line = self._replace_convenience_variables(line)

 return line

 def onecmd(self, line):
 """Interpret the argument as though it had been typed in response
 to the prompt.

 Checks whether this line is typed at the normal prompt or in
 a breakpoint command list definition.
 """
 if not self.commands_defining:
 if line.startswith('_pdbcmd'):
 command, arg, line = self.parseline(line)
 if hasattr(self, command):
 return getattr(self, command)(arg)
 return cmd.Cmd.onecmd(self, line)
 else:
 return self.handle_command_def(line)

 def handle_command_def(self, line):
 """Handles one command line during command list definition."""
 cmd, arg, line = self.parseline(line)
 if not cmd:
 return False
 if cmd == 'end':
 return True # end of cmd list
 elif cmd == 'EOF':
 self.message('')
 return True # end of cmd list
 cmdlist = self.commands[self.commands_bnum]
 if cmd == 'silent':
 cmdlist.append('_pdbcmd_silence_frame_status')
 return False # continue to handle other cmd def in the cmd list
 if arg:
 cmdlist.append(cmd+' '+arg)
 else:
 cmdlist.append(cmd)
 # Determine if we must stop
 try:
 func = getattr(self, 'do_' + cmd)
 except AttributeError:
 func = self.default
 # one of the resuming commands
 if func.__name__ in self.commands_resuming:
 return True
 return False

 def _colorize_code(self, code):
 if self.colorize and _pyrepl:
 colors = list(_pyrepl.utils.gen_colors(code))
 chars, _ = _pyrepl.utils.disp_str(code, colors=colors, force_color=True)
 code = "".join(chars)
 return code

 # interface abstraction functions

 def message(self, msg, end='\n'):
 print(msg, end=end, file=self.stdout)

 def error(self, msg):
 print('***', msg, file=self.stdout)

 # convenience variables

 def set_convenience_variable(self, frame, name, value):
 if '__pdb_convenience_variables' not in frame.f_globals:
 frame.f_globals['__pdb_convenience_variables'] = {}
 frame.f_globals['__pdb_convenience_variables'][name] = value

 # Generic completion functions. Individual complete_foo methods can be
 # assigned below to one of these functions.

 @property
 def rlcompleter(self):
 """Return the `Completer` class from `rlcompleter`, while avoiding the
 side effects of changing the completer from `import rlcompleter`.

 This is a compromise between GH-138860 and GH-139289. If GH-139289 is
 fixed, then we don't need this and we can just `import rlcompleter` in
 `Pdb.__init__`.
 """
 if not hasattr(self, "_rlcompleter"):
 try:
 import readline
 except ImportError:
 # readline is not available, just get the Completer
 from rlcompleter import Completer
 self._rlcompleter = Completer
 else:
 # importing rlcompleter could have side effect of changing
 # the current completer, we need to restore it
 prev_completer = readline.get_completer()
 from rlcompleter import Completer
 self._rlcompleter = Completer
 readline.set_completer(prev_completer)
 return self._rlcompleter

 def completenames(self, text, line, begidx, endidx):
 # Overwrite completenames() of cmd so for the command completion,
 # if no current command matches, check for expressions as well
 commands = super().completenames(text, line, begidx, endidx)
 for alias in self.aliases:
 if alias.startswith(text):
 commands.append(alias)
 if commands:
 return commands
 else:
 expressions = self._complete_expression(text, line, begidx, endidx)
 if expressions:
 return expressions
 return self.completedefault(text, line, begidx, endidx)

 def _complete_location(self, text, line, begidx, endidx):
 # Complete a file/module/function location for break/tbreak/clear.
 if line.strip().endswith((':', ',')):
 # Here comes a line number or a condition which we can't complete.
 return []
 # First, try to find matching functions (i.e. expressions).
 try:
 ret = self._complete_expression(text, line, begidx, endidx)
 except Exception:
 ret = []
 # Then, try to complete file names as well.
 globs = glob.glob(glob.escape(text) + '*')
 for fn in globs:
 if os.path.isdir(fn):
 ret.append(fn + '/')
 elif os.path.isfile(fn) and fn.lower().endswith(('.py', '.pyw')):
 ret.append(fn + ':')
 return ret

 def _complete_bpnumber(self, text, line, begidx, endidx):
 # Complete a breakpoint number. (This would be more helpful if we could
 # display additional info along with the completions, such as file/line
 # of the breakpoint.)
 return [str(i) for i, bp in enumerate(bdb.Breakpoint.bpbynumber)
 if bp is not None and str(i).startswith(text)]

 def _complete_expression(self, text, line, begidx, endidx):
 # Complete an arbitrary expression.
 if not self.curframe:
 return []
 # Collect globals and locals. It is usually not really sensible to also
 # complete builtins, and they clutter the namespace quite heavily, so we
 # leave them out.
 ns = {**self.curframe.f_globals, **self.curframe.f_locals}
 if '.' in text:
 # Walk an attribute chain up to the last part, similar to what
 # rlcompleter does. This will bail if any of the parts are not
 # simple attribute access, which is what we want.
 dotted = text.split('.')
 try:
 if dotted[0].startswith('$'):
 obj = self.curframe.f_globals['__pdb_convenience_variables'][dotted[0][1:]]
 else:
 obj = ns[dotted[0]]
 for part in dotted[1:-1]:
 obj = getattr(obj, part)
 except (KeyError, AttributeError):
 return []
 prefix = '.'.join(dotted[:-1]) + '.'
 return [prefix + n for n in dir(obj) if n.startswith(dotted[-1])]
 else:
 if text.startswith("$"):
 # Complete convenience variables
 conv_vars = self.curframe.f_globals.get('__pdb_convenience_variables', {})
 return [f"${name}" for name in conv_vars if name.startswith(text[1:])]
 # Complete a simple name.
 return [n for n in ns.keys() if n.startswith(text)]

 def _complete_indentation(self, text, line, begidx, endidx):
 try:
 import readline
 except ImportError:
 return []
 # Fill in spaces to form a 4-space indent
 return [' ' * (4 - readline.get_begidx() % 4)]

 def complete_multiline_names(self, text, line, begidx, endidx):
 # If text is space-only, the user entered <tab> before any text.
 # That normally means they want to indent the current line.
 if not text.strip():
 return self._complete_indentation(text, line, begidx, endidx)
 return self.completedefault(text, line, begidx, endidx)

 def completedefault(self, text, line, begidx, endidx):
 if text.startswith("$"):
 # Complete convenience variables
 conv_vars = self.curframe.f_globals.get('__pdb_convenience_variables', {})
 return [f"${name}" for name in conv_vars if name.startswith(text[1:])]

 state = 0
 matches = []
 completer = self.rlcompleter(self.curframe.f_globals | self.curframe.f_locals)
 while (match := completer.complete(text, state)) is not None:
 matches.append(match)
 state += 1
 return matches

 @contextmanager
 def _enable_rlcompleter(self, ns):
 try:
 import readline
 except ImportError:
 yield
 return

 try:
 completer = self.rlcompleter(ns)
 old_completer = readline.get_completer()
 readline.set_completer(completer.complete)
 yield
 finally:
 readline.set_completer(old_completer)

 # Pdb meta commands, only intended to be used internally by pdb

 def _pdbcmd_print_frame_status(self, arg):
 self.print_stack_trace(0)
 self._validate_file_mtime()
 self._show_display()

 def _pdbcmd_silence_frame_status(self, arg):
 if self.cmdqueue and self.cmdqueue[-1] == '_pdbcmd_print_frame_status':
 self.cmdqueue.pop()

 def _pdbcmd_restore_lastcmd(self, arg):
 self.lastcmd = arg

 # Command definitions, called by cmdloop()
 # The argument is the remaining string on the command line
 # Return true to exit from the command loop

 def do_commands(self, arg):
 """(Pdb) commands [bpnumber]
 (com) ...
 (com) end
 (Pdb)

 Specify a list of commands for breakpoint number bpnumber.
 The commands themselves are entered on the following lines.
 Type a line containing just 'end' to terminate the commands.
 The commands are executed when the breakpoint is hit.

 To remove all commands from a breakpoint, type commands and
 follow it immediately with end; that is, give no commands.

 With no bpnumber argument, commands refers to the last
 breakpoint set.

 You can use breakpoint commands to start your program up
 again. Simply use the continue command, or step, or any other
 command that resumes execution.

 Specifying any command resuming execution (currently continue,
 step, next, return, jump, quit and their abbreviations)
 terminates the command list (as if that command was
 immediately followed by end). This is because any time you
 resume execution (even with a simple next or step), you may
 encounter another breakpoint -- which could have its own
 command list, leading to ambiguities about which list to
 execute.

 If you use the 'silent' command in the command list, the usual
 message about stopping at a breakpoint is not printed. This
 may be desirable for breakpoints that are to print a specific
 message and then continue. If none of the other commands
 print anything, you will see no sign that the breakpoint was
 reached.
 """
 if not arg:
 for bp in reversed(bdb.Breakpoint.bpbynumber):
 if bp is None:
 continue
 bnum = bp.number
 break
 else:
 self.error('cannot set commands: no existing breakpoint')
 return
 else:
 try:
 bnum = int(arg)
 except:
 self._print_invalid_arg(arg)
 return
 try:
 self.get_bpbynumber(bnum)
 except ValueError as err:
 self.error('cannot set commands: %s' % err)
 return

 self.commands_bnum = bnum
 # Save old definitions for the case of a keyboard interrupt.
 if bnum in self.commands:
 old_commands = self.commands[bnum]
 else:
 old_commands = None
 self.commands[bnum] = []

 prompt_back = self.prompt
 self.prompt = '(com) '
 self.commands_defining = True
 try:
 self.cmdloop()
 except KeyboardInterrupt:
 # Restore old definitions.
 if old_commands:
 self.commands[bnum] = old_commands
 else:
 del self.commands[bnum]
 self.error('command definition aborted, old commands restored')
 finally:
 self.commands_defining = False
 self.prompt = prompt_back

 complete_commands = _complete_bpnumber

 def do_break(self, arg, temporary=False):
 """b(reak) [ ([filename:]lineno | function) [, condition] ]

 Without argument, list all breaks.

 With a line number argument, set a break at this line in the
 current file. With a function name, set a break at the first
 executable line of that function. If a second argument is
 present, it is a string specifying an expression which must
 evaluate to true before the breakpoint is honored.

 The line number may be prefixed with a filename and a colon,
 to specify a breakpoint in another file (probably one that
 hasn't been loaded yet). The file is searched for on
 sys.path; the .py suffix may be omitted.
 """
 if not arg:
 if self.breaks: # There's at least one
 self.message("Num Type Disp Enb Where")
 for bp in bdb.Breakpoint.bpbynumber:
 if bp:
 self.message(bp.bpformat())
 return
 # parse arguments; comma has lowest precedence
 # and cannot occur in filename
 filename = None
 lineno = None
 cond = None
 module_globals = None
 comma = arg.find(',')
 if comma > 0:
 # parse stuff after comma: "condition"
 cond = arg[comma+1:].lstrip()
 if err := self._compile_error_message(cond):
 self.error('Invalid condition %s: %r' % (cond, err))
 return
 arg = arg[:comma].rstrip()
 # parse stuff before comma: [filename:]lineno | function
 colon = arg.rfind(':')
 funcname = None
 if colon >= 0:
 filename = arg[:colon].rstrip()
 f = self.lookupmodule(filename)
 if not f:
 self.error('%r not found from sys.path' % filename)
 return
 else:
 filename = f
 arg = arg[colon+1:].lstrip()
 try:
 lineno = int(arg)
 except ValueError:
 self.error('Bad lineno: %s' % arg)
 return
 else:
 # no colon; can be lineno or function
 try:
 lineno = int(arg)
 except ValueError:
 try:
 func = eval(arg,
 self.curframe.f_globals,
 self.curframe.f_locals)
 except:
 func = arg
 try:
 if hasattr(func, '__func__'):
 func = func.__func__
 code = func.__code__
 #use co_name to identify the bkpt (function names
 #could be aliased, but co_name is invariant)
 funcname = code.co_name
 lineno = find_first_executable_line(code)
 filename = code.co_filename
 module_globals = func.__globals__
 except:
 # last thing to try
 (ok, filename, ln) = self.lineinfo(arg)
 if not ok:
 self.error('The specified object %r is not a function '
 'or was not found along sys.path.' % arg)
 return
 funcname = ok # ok contains a function name
 lineno = int(ln)
 if not filename:
 filename = self.defaultFile()
 filename = self.canonic(filename)
 # Check for reasonable breakpoint
 line = self.checkline(filename, lineno, module_globals)
 if line:
 # now set the break point
 err = self.set_break(filename, line, temporary, cond, funcname)
 if err:
 self.error(err)
 else:
 bp = self.get_breaks(filename, line)[-1]
 self.message("Breakpoint %d at %s:%d" %
 (bp.number, bp.file, bp.line))

 # To be overridden in derived debuggers
 def defaultFile(self):
 """Produce a reasonable default."""
 filename = self.curframe.f_code.co_filename
 if filename == '<string>' and self.mainpyfile:
 filename = self.mainpyfile
 return filename

 do_b = do_break

 complete_break = _complete_location
 complete_b = _complete_location

 def do_tbreak(self, arg):
 """tbreak [ ([filename:]lineno | function) [, condition] ]

 Same arguments as break, but sets a temporary breakpoint: it
 is automatically deleted when first hit.
 """
 self.do_break(arg, True)

 complete_tbreak = _complete_location

 def lineinfo(self, identifier):
 failed = (None, None, None)
 # Input is identifier, may be in single quotes
 idstring = identifier.split("'")
 if len(idstring) == 1:
 # not in single quotes
 id = idstring[0].strip()
 elif len(idstring) == 3:
 # quoted
 id = idstring[1].strip()
 else:
 return failed
 if id == '': return failed
 parts = id.split('.')
 # Protection for derived debuggers
 if parts[0] == 'self':
 del parts[0]
 if len(parts) == 0:
 return failed
 # Best first guess at file to look at
 fname = self.defaultFile()
 if len(parts) == 1:
 item = parts[0]
 else:
 # More than one part.
 # First is module, second is method/class
 f = self.lookupmodule(parts[0])
 if f:
 fname = f
 item = parts[1]
 else:
 return failed
 answer = find_function(item, self.canonic(fname))
 return answer or failed

 def checkline(self, filename, lineno, module_globals=None):
 """Check whether specified line seems to be executable.

 Return `lineno` if it is, 0 if not (e.g. a docstring, comment, blank
 line or EOF). Warning: testing is not comprehensive.
 """
 # this method should be callable before starting debugging, so default
 # to "no globals" if there is no current frame
 frame = self.curframe
 if module_globals is None:
 module_globals = frame.f_globals if frame else None
 line = linecache.getline(filename, lineno, module_globals)
 if not line:
 self.message('End of file')
 return 0
 line = line.strip()
 # Don't allow setting breakpoint at a blank line
 if (not line or (line[0] == '#') or
 (line[:3] == '"""') or line[:3] == "'''"):
 self.error('Blank or comment')
 return 0
 return lineno

 def do_enable(self, arg):
 """enable bpnumber [bpnumber ...]

 Enables the breakpoints given as a space separated list of
 breakpoint numbers.
 """
 if not arg:
 self._print_invalid_arg(arg)
 return
 args = arg.split()
 for i in args:
 try:
 bp = self.get_bpbynumber(i)
 except ValueError as err:
 self.error(err)
 else:
 bp.enable()
 self.message('Enabled %s' % bp)

 complete_enable = _complete_bpnumber

 def do_disable(self, arg):
 """disable bpnumber [bpnumber ...]

 Disables the breakpoints given as a space separated list of
 breakpoint numbers. Disabling a breakpoint means it cannot
 cause the program to stop execution, but unlike clearing a
 breakpoint, it remains in the list of breakpoints and can be
 (re-)enabled.
 """
 if not arg:
 self._print_invalid_arg(arg)
 return
 args = arg.split()
 for i in args:
 try:
 bp = self.get_bpbynumber(i)
 except ValueError as err:
 self.error(err)
 else:
 bp.disable()
 self.message('Disabled %s' % bp)

 complete_disable = _complete_bpnumber

 def do_condition(self, arg):
 """condition bpnumber [condition]

 Set a new condition for the breakpoint, an expression which
 must evaluate to true before the breakpoint is honored. If
 condition is absent, any existing condition is removed; i.e.,
 the breakpoint is made unconditional.
 """
 if not arg:
 self._print_invalid_arg(arg)
 return
 args = arg.split(' ', 1)
 try:
 cond = args[1]
 if err := self._compile_error_message(cond):
 self.error('Invalid condition %s: %r' % (cond, err))
 return
 except IndexError:
 cond = None
 try:
 bp = self.get_bpbynumber(args[0].strip())
 except IndexError:
 self.error('Breakpoint number expected')
 except ValueError as err:
 self.error(err)
 else:
 bp.cond = cond
 if not cond:
 self.message('Breakpoint %d is now unconditional.' % bp.number)
 else:
 self.message('New condition set for breakpoint %d.' % bp.number)

 complete_condition = _complete_bpnumber

 def do_ignore(self, arg):
 """ignore bpnumber [count]

 Set the ignore count for the given breakpoint number. If
 count is omitted, the ignore count is set to 0. A breakpoint
 becomes active when the ignore count is zero. When non-zero,
 the count is decremented each time the breakpoint is reached
 and the breakpoint is not disabled and any associated
 condition evaluates to true.
 """
 if not arg:
 self._print_invalid_arg(arg)
 return
 args = arg.split()
 if not args:
 self.error('Breakpoint number expected')
 return
 if len(args) == 1:
 count = 0
 elif len(args) == 2:
 try:
 count = int(args[1])
 except ValueError:
 self._print_invalid_arg(arg)
 return
 else:
 self._print_invalid_arg(arg)
 return
 try:
 bp = self.get_bpbynumber(args[0].strip())
 except ValueError as err:
 self.error(err)
 else:
 bp.ignore = count
 if count > 0:
 if count > 1:
 countstr = '%d crossings' % count
 else:
 countstr = '1 crossing'
 self.message('Will ignore next %s of breakpoint %d.' %
 (countstr, bp.number))
 else:
 self.message('Will stop next time breakpoint %d is reached.'
 % bp.number)

 complete_ignore = _complete_bpnumber

 def _prompt_for_confirmation(self, prompt, default):
 try:
 reply = input(prompt)
 except EOFError:
 reply = default
 return reply.strip().lower()

 def do_clear(self, arg):
 """cl(ear) [filename:lineno | bpnumber ...]

 With a space separated list of breakpoint numbers, clear
 those breakpoints. Without argument, clear all breaks (but
 first ask confirmation). With a filename:lineno argument,
 clear all breaks at that line in that file.
 """
 if not arg:
 reply = self._prompt_for_confirmation(
 'Clear all breaks? ',
 default='no',
 )
 if reply in ('y', 'yes'):
 bplist = [bp for bp in bdb.Breakpoint.bpbynumber if bp]
 self.clear_all_breaks()
 for bp in bplist:
 self.message('Deleted %s' % bp)
 return
 if ':' in arg:
 # Make sure it works for "clear C:\foo\bar.py:12"
 i = arg.rfind(':')
 filename = arg[:i]
 arg = arg[i+1:]
 try:
 lineno = int(arg)
 except ValueError:
 err = "Invalid line number (%s)" % arg
 else:
 bplist = self.get_breaks(filename, lineno)[:]
 err = self.clear_break(filename, lineno)
 if err:
 self.error(err)
 else:
 for bp in bplist:
 self.message('Deleted %s' % bp)
 return
 numberlist = arg.split()
 for i in numberlist:
 try:
 bp = self.get_bpbynumber(i)
 except ValueError as err:
 self.error(err)
 else:
 self.clear_bpbynumber(i)
 self.message('Deleted %s' % bp)
 do_cl = do_clear # 'c' is already an abbreviation for 'continue'

 complete_clear = _complete_location
 complete_cl = _complete_location

 def do_where(self, arg):
 """w(here) [count]

 Print a stack trace. If count is not specified, print the full stack.
 If count is 0, print the current frame entry. If count is positive,
 print count entries from the most recent frame. If count is negative,
 print -count entries from the least recent frame.
 An arrow indicates the "current frame", which determines the
 context of most commands. 'bt' is an alias for this command.
 """
 if not arg:
 count = None
 else:
 try:
 count = int(arg)
 except ValueError:
 self.error('Invalid count (%s)' % arg)
 return
 self.print_stack_trace(count)
 do_w = do_where
 do_bt = do_where

 def _select_frame(self, number):
 assert 0 <= number < len(self.stack)
 self.curindex = number
 self.curframe = self.stack[self.curindex][0]
 self.set_convenience_variable(self.curframe, '_frame', self.curframe)
 self.print_stack_entry(self.stack[self.curindex])
 self.lineno = None

 def do_exceptions(self, arg):
 """exceptions [number]

 List or change current exception in an exception chain.

 Without arguments, list all the current exception in the exception
 chain. Exceptions will be numbered, with the current exception indicated
 with an arrow.

 If given an integer as argument, switch to the exception at that index.
 """
 if not self._chained_exceptions:
 self.message(
 "Did not find chained exceptions. To move between"
 " exceptions, pdb/post_mortem must be given an exception"
 " object rather than a traceback."
 )
 return
 if not arg:
 for ix, exc in enumerate(self._chained_exceptions):
 prompt = ">" if ix == self._chained_exception_index else " "
 rep = repr(exc)
 if len(rep) > 80:
 rep = rep[:77] + "..."
 indicator = (
 " -"
 if self._chained_exceptions[ix].__traceback__ is None
 else f"{ix:>3}"
 )
 self.message(f"{prompt} {indicator} {rep}")
 else:
 try:
 number = int(arg)
 except ValueError:
 self.error("Argument must be an integer")
 return
 if 0 <= number < len(self._chained_exceptions):
 if self._chained_exceptions[number].__traceback__ is None:
 self.error("This exception does not have a traceback, cannot jump to it")
 return

 self._chained_exception_index = number
 self.setup(None, self._chained_exceptions[number].__traceback__)
 self.print_stack_entry(self.stack[self.curindex])
 else:
 self.error("No exception with that number")

 def do_up(self, arg):
 """u(p) [count]

 Move the current frame count (default one) levels up in the
 stack trace (to an older frame).
 """
 if self.curindex == 0:
 self.error('Oldest frame')
 return
 try:
 count = int(arg or 1)
 except ValueError:
 self.error('Invalid frame count (%s)' % arg)
 return
 if count < 0:
 newframe = 0
 else:
 newframe = max(0, self.curindex - count)
 self._select_frame(newframe)
 do_u = do_up

 def do_down(self, arg):
 """d(own) [count]

 Move the current frame count (default one) levels down in the
 stack trace (to a newer frame).
 """
 if self.curindex + 1 == len(self.stack):
 self.error('Newest frame')
 return
 try:
 count = int(arg or 1)
 except ValueError:
 self.error('Invalid frame count (%s)' % arg)
 return
 if count < 0:
 newframe = len(self.stack) - 1
 else:
 newframe = min(len(self.stack) - 1, self.curindex + count)
 self._select_frame(newframe)
 do_d = do_down

 def do_until(self, arg):
 """unt(il) [lineno]

 Without argument, continue execution until the line with a
 number greater than the current one is reached. With a line
 number, continue execution until a line with a number greater
 or equal to that is reached. In both cases, also stop when
 the current frame returns.
 """
 if arg:
 try:
 lineno = int(arg)
 except ValueError:
 self.error('Error in argument: %r' % arg)
 return
 if lineno <= self.curframe.f_lineno:
 self.error('"until" line number is smaller than current '
 'line number')
 return
 else:
 lineno = None
 self.set_until(self.curframe, lineno)
 return 1
 do_unt = do_until

 def do_step(self, arg):
 """s(tep)

 Execute the current line, stop at the first possible occasion
 (either in a function that is called or in the current
 function).
 """
 if arg:
 self._print_invalid_arg(arg)
 return
 self.set_step()
 return 1
 do_s = do_step

 def do_next(self, arg):
 """n(ext)

 Continue execution until the next line in the current function
 is reached or it returns.
 """
 if arg:
 self._print_invalid_arg(arg)
 return
 self.set_next(self.curframe)
 return 1
 do_n = do_next

 def do_run(self, arg):
 """run [args...]

 Restart the debugged python program. If a string is supplied
 it is split with "shlex", and the result is used as the new
 sys.argv. History, breakpoints, actions and debugger options
 are preserved. "restart" is an alias for "run".
 """
 if self.mode == 'inline':
 self.error('run/restart command is disabled when pdb is running in inline mode.\n'
 'Use the command line interface to enable restarting your program\n'
 'e.g. "python -m pdb myscript.py"')
 return
 if arg:
 import shlex
 argv0 = sys.argv[0:1]
 try:
 sys.argv = shlex.split(arg)
 except ValueError as e:
 self.error('Cannot run %s: %s' % (arg, e))
 return
 sys.argv[:0] = argv0
 # this is caught in the main debugger loop
 raise Restart

 do_restart = do_run

 def do_return(self, arg):
 """r(eturn)

 Continue execution until the current function returns.
 """
 if arg:
 self._print_invalid_arg(arg)
 return
 self.set_return(self.curframe)
 return 1
 do_r = do_return

 def do_continue(self, arg):
 """c(ont(inue))

 Continue execution, only stop when a breakpoint is encountered.
 """
 if arg:
 self._print_invalid_arg(arg)
 return
 if not self.nosigint:
 try:
 Pdb._previous_sigint_handler = \
 signal.signal(signal.SIGINT, self.sigint_handler)
 except ValueError:
 # ValueError happens when do_continue() is invoked from
 # a non-main thread in which case we just continue without
 # SIGINT set. Would printing a message here (once) make
 # sense?
 pass
 self.set_continue()
 return 1
 do_c = do_cont = do_continue

 def do_jump(self, arg):
 """j(ump) lineno

 Set the next line that will be executed. Only available in
 the bottom-most frame. This lets you jump back and execute
 code again, or jump forward to skip code that you don't want
 to run.

 It should be noted that not all jumps are allowed -- for
 instance it is not possible to jump into the middle of a
 for loop or out of a finally clause.
 """
 if not arg:
 self._print_invalid_arg(arg)
 return
 if self.curindex + 1 != len(self.stack):
 self.error('You can only jump within the bottom frame')
 return
 try:
 arg = int(arg)
 except ValueError:
 self.error("The 'jump' command requires a line number")
 else:
 try:
 # Do the jump, fix up our copy of the stack, and display the
 # new position
 self.curframe.f_lineno = arg
 self.stack[self.curindex] = self.stack[self.curindex][0], arg
 self.print_stack_entry(self.stack[self.curindex])
 except ValueError as e:
 self.error('Jump failed: %s' % e)
 do_j = do_jump

 def _create_recursive_debugger(self):
 return Pdb(self.completekey, self.stdin, self.stdout)

 def do_debug(self, arg):
 """debug code

 Enter a recursive debugger that steps through the code
 argument (which is an arbitrary expression or statement to be
 executed in the current environment).
 """
 if not arg:
 self._print_invalid_arg(arg)
 return
 self.stop_trace()
 globals = self.curframe.f_globals
 locals = self.curframe.f_locals
 p = self._create_recursive_debugger()
 p.prompt = "(%s) " % self.prompt.strip()
 self.message("ENTERING RECURSIVE DEBUGGER")
 try:
 sys.call_tracing(p.run, (arg, globals, locals))
 except Exception:
 self._error_exc()
 self.message("LEAVING RECURSIVE DEBUGGER")
 self.start_trace()
 self.lastcmd = p.lastcmd

 complete_debug = _complete_expression

 def do_quit(self, arg):
 """q(uit) | exit

 Quit from the debugger. The program being executed is aborted.
 """
 # Show prompt to kill process when in 'inline' mode and if pdb was not
 # started from an interactive console. The attribute sys.ps1 is only
 # defined if the interpreter is in interactive mode.
 if self.mode == 'inline' and not hasattr(sys, 'ps1'):
 while True:
 try:
 reply = input('Quitting pdb will kill the process. Quit anyway? [y/n] ')
 reply = reply.lower().strip()
 except EOFError:
 reply = 'y'
 self.message('')
 if reply == 'y' or reply == '':
 sys.exit(1)
 elif reply.lower() == 'n':
 return

 self._user_requested_quit = True
 self.set_quit()
 return 1

 do_q = do_quit
 do_exit = do_quit

 def do_EOF(self, arg):
 """EOF

 Handles the receipt of EOF as a command.
 """
 self.message('')
 return self.do_quit(arg)

 def do_args(self, arg):
 """a(rgs)

 Print the argument list of the current function.
 """
 if arg:
 self._print_invalid_arg(arg)
 return
 co = self.curframe.f_code
 dict = self.curframe.f_locals
 n = co.co_argcount + co.co_kwonlyargcount
 if co.co_flags & inspect.CO_VARARGS: n = n+1
 if co.co_flags & inspect.CO_VARKEYWORDS: n = n+1
 for i in range(n):
 name = co.co_varnames[i]
 if name in dict:
 self.message('%s = %s' % (name, self._safe_repr(dict[name], name)))
 else:
 self.message('%s = *** undefined ***' % (name,))
 do_a = do_args

 def do_retval(self, arg):
 """retval

 Print the return value for the last return of a function.
 """
 if arg:
 self._print_invalid_arg(arg)
 return
 if '__return__' in self.curframe.f_locals:
 self.message(self._safe_repr(self.curframe.f_locals['__return__'], "retval"))
 else:
 self.error('Not yet returned!')
 do_rv = do_retval

 def _getval(self, arg):
 try:
 return eval(arg, self.curframe.f_globals, self.curframe.f_locals)
 except:
 self._error_exc()
 raise

 def _getval_except(self, arg, frame=None):
 try:
 if frame is None:
 return eval(arg, self.curframe.f_globals, self.curframe.f_locals)
 else:
 return eval(arg, frame.f_globals, frame.f_locals)
 except BaseException as exc:
 return _rstr('** raised %s **' % self._format_exc(exc))

 def _error_exc(self):
 exc = sys.exception()
 self.error(self._format_exc(exc))

 def _msg_val_func(self, arg, func):
 try:
 val = self._getval(arg)
 except:
 return # _getval() has displayed the error
 try:
 self.message(func(val))
 except:
 self._error_exc()

 def _safe_repr(self, obj, expr):
 try:
 return repr(obj)
 except Exception as e:
 return _rstr(f"*** repr({expr}) failed: {self._format_exc(e)} ***")

 def do_p(self, arg):
 """p expression

 Print the value of the expression.
 """
 if not arg:
 self._print_invalid_arg(arg)
 return
 self._msg_val_func(arg, repr)

 def do_pp(self, arg):
 """pp expression

 Pretty-print the value of the expression.
 """
 if not arg:
 self._print_invalid_arg(arg)
 return
 self._msg_val_func(arg, pprint.pformat)

 complete_print = _complete_expression
 complete_p = _complete_expression
 complete_pp = _complete_expression

 def do_list(self, arg):
 """l(ist) [first[, last] | .]

 List source code for the current file. Without arguments,
 list 11 lines around the current line or continue the previous
 listing. With . as argument, list 11 lines around the current
 line. With one argument, list 11 lines starting at that line.
 With two arguments, list the given range; if the second
 argument is less than the first, it is a count.

 The current line in the current frame is indicated by "->".
 If an exception is being debugged, the line where the
 exception was originally raised or propagated is indicated by
 ">>", if it differs from the current line.
 """
 self.lastcmd = 'list'
 last = None
 if arg and arg != '.':
 try:
 if ',' in arg:
 first, last = arg.split(',')
 first = int(first.strip())
 last = int(last.strip())
 if last < first:
 # assume it's a count
 last = first + last
 else:
 first = int(arg.strip())
 first = max(1, first - 5)
 except ValueError:
 self.error('Error in argument: %r' % arg)
 return
 elif self.lineno is None or arg == '.':
 first = max(1, self.curframe.f_lineno - 5)
 else:
 first = self.lineno + 1
 if last is None:
 last = first + 10
 filename = self.curframe.f_code.co_filename
 breaklist = self.get_file_breaks(filename)
 try:
 lines = linecache.getlines(filename, self.curframe.f_globals)
 self._print_lines(lines[first-1:last], first, breaklist,
 self.curframe)
 self.lineno = min(last, len(lines))
 if len(lines) < last:
 self.message('[EOF]')
 except KeyboardInterrupt:
 pass
 self._validate_file_mtime()
 do_l = do_list

 def do_longlist(self, arg):
 """ll | longlist

 List the whole source code for the current function or frame.
 """
 if arg:
 self._print_invalid_arg(arg)
 return
 filename = self.curframe.f_code.co_filename
 breaklist = self.get_file_breaks(filename)
 try:
 lines, lineno = self._getsourcelines(self.curframe)
 except OSError as err:
 self.error(err)
 return
 self._print_lines(lines, lineno, breaklist, self.curframe)
 self._validate_file_mtime()
 do_ll = do_longlist

 def do_source(self, arg):
 """source expression

 Try to get source code for the given object and display it.
 """
 if not arg:
 self._print_invalid_arg(arg)
 return
 try:
 obj = self._getval(arg)
 except:
 return
 try:
 lines, lineno = self._getsourcelines(obj)
 except (OSError, TypeError) as err:
 self.error(err)
 return
 self._print_lines(lines, lineno)

 complete_source = _complete_expression

 def _print_lines(self, lines, start, breaks=(), frame=None):
 """Print a range of lines."""
 if frame:
 current_lineno = frame.f_lineno
 exc_lineno = self.tb_lineno.get(frame, -1)
 else:
 current_lineno = exc_lineno = -1
 for lineno, line in enumerate(lines, start):
 s = str(lineno).rjust(3)
 if len(s) < 4:
 s += ' '
 if lineno in breaks:
 s += 'B'
 else:
 s += ' '
 if lineno == current_lineno:
 s += '->'
 elif lineno == exc_lineno:
 s += '>>'
 if self.colorize:
 line = self._colorize_code(line)
 self.message(s + '\t' + line.rstrip())

 def do_whatis(self, arg):
 """whatis expression

 Print the type of the argument.
 """
 if not arg:
 self._print_invalid_arg(arg)
 return
 try:
 value = self._getval(arg)
 except:
 # _getval() already printed the error
 return
 code = None
 # Is it an instance method?
 try:
 code = value.__func__.__code__
 except Exception:
 pass
 if code:
 self.message('Method %s' % code.co_name)
 return
 # Is it a function?
 try:
 code = value.__code__
 except Exception:
 pass
 if code:
 self.message('Function %s' % code.co_name)
 return
 # Is it a class?
 if value.__class__ is type:
 self.message('Class %s.%s' % (value.__module__, value.__qualname__))
 return
 # None of the above...
 self.message(type(value))

 complete_whatis = _complete_expression

 def do_display(self, arg):
 """display [expression]

 Display the value of the expression if it changed, each time execution
 stops in the current frame.

 Without expression, list all display expressions for the current frame.
 """
 if not arg:
 if self.displaying:
 self.message('Currently displaying:')
 for key, val in self.displaying.get(self.curframe, {}).items():
 self.message('%s: %s' % (key, self._safe_repr(val, key)))
 else:
 self.message('No expression is being displayed')
 else:
 if err := self._compile_error_message(arg):
 self.error('Unable to display %s: %r' % (arg, err))
 else:
 val = self._getval_except(arg)
 self.displaying.setdefault(self.curframe, {})[arg] = val
 self.message('display %s: %s' % (arg, self._safe_repr(val, arg)))

 complete_display = _complete_expression

 def do_undisplay(self, arg):
 """undisplay [expression]

 Do not display the expression any more in the current frame.

 Without expression, clear all display expressions for the current frame.
 """
 if arg:
 try:
 del self.displaying.get(self.curframe, {})[arg]
 except KeyError:
 self.error('not displaying %s' % arg)
 else:
 self.displaying.pop(self.curframe, None)

 def complete_undisplay(self, text, line, begidx, endidx):
 return [e for e in self.displaying.get(self.curframe, {})
 if e.startswith(text)]

 def do_interact(self, arg):
 """interact

 Start an interactive interpreter whose global namespace
 contains all the (global and local) names found in the current scope.
 """
 ns = {**self.curframe.f_globals, **self.curframe.f_locals}
 console = _PdbInteractiveConsole(ns, message=self.message)
 banner = "*pdb interact start*"
 exitmsg = "*exit from pdb interact command*"
 if self.pyrepl_input is not None:
 from _pyrepl.simple_interact import run_multiline_interactive_console
 self.message(banner)
 try:
 run_multiline_interactive_console(console)
 except SystemExit:
 pass
 self.message(exitmsg)
 else:
 with self._enable_rlcompleter(ns):
 console.interact(banner=banner,
 exitmsg=exitmsg)

 def do_alias(self, arg):
 """alias [name [command]]

 Create an alias called 'name' that executes 'command'. The
 command must *not* be enclosed in quotes. Replaceable
 parameters can be indicated by %1, %2, and so on, while %* is
 replaced by all the parameters. If no command is given, the
 current alias for name is shown. If no name is given, all
 aliases are listed.

 Aliases may be nested and can contain anything that can be
 legally typed at the pdb prompt. Note! You *can* override
 internal pdb commands with aliases! Those internal commands
 are then hidden until the alias is removed. Aliasing is
 recursively applied to the first word of the command line; all
 other words in the line are left alone.

 As an example, here are two useful aliases (especially when
 placed in the .pdbrc file):

 # Print instance variables (usage "pi classInst")
 alias pi for k in %1.__dict__.keys(): print("%1.",k,"=",%1.__dict__[k])
 # Print instance variables in self
 alias ps pi self
 """
 args = arg.split()
 if len(args) == 0:
 keys = sorted(self.aliases.keys())
 for alias in keys:
 self.message("%s = %s" % (alias, self.aliases[alias]))
 return
 if len(args) == 1:
 if args[0] in self.aliases:
 self.message("%s = %s" % (args[0], self.aliases[args[0]]))
 else:
 self.error(f"Unknown alias '{args[0]}'")
 else:
 # Do a validation check to make sure no replaceable parameters
 # are skipped if %* is not used.
 alias = ' '.join(args[1:])
 if '%*' not in alias:
 consecutive = True
 for idx in range(1, 10):
 if f'%{idx}' not in alias:
 consecutive = False
 if f'%{idx}' in alias and not consecutive:
 self.error("Replaceable parameters must be consecutive")
 return
 self.aliases[args[0]] = alias

 def do_unalias(self, arg):
 """unalias name

 Delete the specified alias.
 """
 args = arg.split()
 if len(args) == 0:
 self._print_invalid_arg(arg)
 return
 if args[0] in self.aliases:
 del self.aliases[args[0]]

 def complete_unalias(self, text, line, begidx, endidx):
 return [a for a in self.aliases if a.startswith(text)]

 # List of all the commands making the program resume execution.
 commands_resuming = ['do_continue', 'do_step', 'do_next', 'do_return',
 'do_until', 'do_quit', 'do_jump']

 # Print a traceback starting at the top stack frame.
 # The most recently entered frame is printed last;
 # this is different from dbx and gdb, but consistent with
 # the Python interpreter's stack trace.
 # It is also consistent with the up/down commands (which are
 # compatible with dbx and gdb: up moves towards 'main()'
 # and down moves towards the most recent stack frame).
 # * if count is None, prints the full stack
 # * if count = 0, prints the current frame entry
 # * if count < 0, prints -count least recent frame entries
 # * if count > 0, prints count most recent frame entries

 def print_stack_trace(self, count=None):
 if count is None:
 stack_to_print = self.stack
 elif count == 0:
 stack_to_print = [self.stack[self.curindex]]
 elif count < 0:
 stack_to_print = self.stack[:-count]
 else:
 stack_to_print = self.stack[-count:]
 try:
 for frame_lineno in stack_to_print:
 self.print_stack_entry(frame_lineno)
 except KeyboardInterrupt:
 pass

 def print_stack_entry(self, frame_lineno, prompt_prefix=None):
 if prompt_prefix is None:
 prompt_prefix = line_prefix
 frame, lineno = frame_lineno
 if frame is self.curframe:
 prefix = '> '
 else:
 prefix = ' '
 stack_entry = self.format_stack_entry(frame_lineno, prompt_prefix)
 if self.colorize:
 lines = stack_entry.split(prompt_prefix, 1)
 if len(lines) > 1:
 # We have some code to display
 lines[1] = self._colorize_code(lines[1])
 stack_entry = prompt_prefix.join(lines)
 self.message(prefix + stack_entry)

 # Provide help

 def do_help(self, arg):
 """h(elp)

 Without argument, print the list of available commands.
 With a command name as argument, print help about that command.
 "help pdb" shows the full pdb documentation.
 "help exec" gives help on the ! command.
 """
 if not arg:
 return cmd.Cmd.do_help(self, arg)
 try:
 try:
 topic = getattr(self, 'help_' + arg)
 return topic()
 except AttributeError:
 command = getattr(self, 'do_' + arg)
 except AttributeError:
 self.error('No help for %r' % arg)
 else:
 if sys.flags.optimize >= 2:
 self.error('No help for %r; please do not run Python with -OO '
 'if you need command help' % arg)
 return
 if command.__doc__ is None:
 self.error('No help for %r; __doc__ string missing' % arg)
 return
 self.message(self._help_message_from_doc(command.__doc__))

 do_h = do_help

 def help_exec(self):
 """(!) statement

 Execute the (one-line) statement in the context of the current
 stack frame. The exclamation point can be omitted unless the
 first word of the statement resembles a debugger command, e.g.:
 (Pdb) ! n=42
 (Pdb)

 To assign to a global variable you must always prefix the command with
 a 'global' command, e.g.:
 (Pdb) global list_options; list_options = ['-l']
 (Pdb)
 """
 self.message((self.help_exec.__doc__ or '').strip())

 def help_pdb(self):
 help()

 # other helper functions

 def lookupmodule(self, filename):
 """Helper function for break/clear parsing -- may be overridden.

 lookupmodule() translates (possibly incomplete) file or module name
 into an absolute file name.

 filename could be in format of:
 * an absolute path like '/path/to/file.py'
 * a relative path like 'file.py' or 'dir/file.py'
 * a module name like 'module' or 'package.module'

 files and modules will be searched in sys.path.
 """
 if not filename.endswith('.py'):
 # A module is passed in so convert it to equivalent file
 filename = filename.replace('.', os.sep) + '.py'

 if os.path.isabs(filename):
 if os.path.exists(filename):
 return filename
 return None

 for dirname in sys.path:
 while os.path.islink(dirname):
 dirname = os.readlink(dirname)
 fullname = os.path.join(dirname, filename)
 if os.path.exists(fullname):
 return fullname
 return None

 def _run(self, target: _ExecutableTarget):
 # When bdb sets tracing, a number of call and line events happen
 # BEFORE debugger even reaches user's code (and the exact sequence of
 # events depends on python version). Take special measures to
 # avoid stopping before reaching the main script (see user_line and
 # user_call for details).
 self._wait_for_mainpyfile = True
 self._user_requested_quit = False

 self.mainpyfile = self.canonic(target.filename)

 # The target has to run in __main__ namespace (or imports from
 # __main__ will break). Clear __main__ and replace with
 # the target namespace.
 import __main__
 __main__.__dict__.clear()
 __main__.__dict__.update(target.namespace)

 # Clear the mtime table for program reruns, assume all the files
 # are up to date.
 self._file_mtime_table.clear()

 self.run(target.code)

 def _format_exc(self, exc: BaseException):
 return traceback.format_exception_only(exc)[-1].strip()

 def _compile_error_message(self, expr):
 """Return the error message as string if compiling `expr` fails."""
 try:
 compile(expr, "<stdin>", "eval")
 except SyntaxError as exc:
 return _rstr(self._format_exc(exc))
 return ""

 def _getsourcelines(self, obj):
 # GH-103319
 # inspect.getsourcelines() returns lineno = 0 for
 # module-level frame which breaks our code print line number
 # This method should be replaced by inspect.getsourcelines(obj)
 # once this bug is fixed in inspect
 lines, lineno = inspect.getsourcelines(obj)
 lineno = max(1, lineno)
 return lines, lineno

 def _help_message_from_doc(self, doc, usage_only=False):
 lines = [line.strip() for line in doc.rstrip().splitlines()]
 if not lines:
 return "No help message found."
 if "" in lines:
 usage_end = lines.index("")
 else:
 usage_end = 1
 formatted = []
 indent = " " * len(self.prompt)
 for i, line in enumerate(lines):
 if i == 0:
 prefix = "Usage: "
 elif i < usage_end:
 prefix = " "
 else:
 if usage_only:
 break
 prefix = ""
 formatted.append(indent + prefix + line)
 return "\n".join(formatted)

 def _print_invalid_arg(self, arg):
 """Return the usage string for a function."""

 if not arg:
 self.error("Argument is required for this command")
 else:
 self.error(f"Invalid argument: {arg}")

 # Yes it's a bit hacky. Get the caller name, get the method based on
 # that name, and get the docstring from that method.
 # This should NOT fail if the caller is a method of this class.
 doc = inspect.getdoc(getattr(self, sys._getframe(1).f_code.co_name))
 if doc is not None:
 self.message(self._help_message_from_doc(doc, usage_only=True))

# Collect all command help into docstring, if not run with -OO

if __doc__ is not None:
 # unfortunately we can't guess this order from the class definition
 _help_order = [
 'help', 'where', 'down', 'up', 'break', 'tbreak', 'clear', 'disable',
 'enable', 'ignore', 'condition', 'commands', 'step', 'next', 'until',
 'jump', 'return', 'retval', 'run', 'continue', 'list', 'longlist',
 'args', 'p', 'pp', 'whatis', 'source', 'display', 'undisplay',
 'interact', 'alias', 'unalias', 'debug', 'quit',
 ]

 for _command in _help_order:
 __doc__ += getattr(Pdb, 'do_' + _command).__doc__.strip() + '\n\n'
 __doc__ += Pdb.help_exec.__doc__

 del _help_order, _command


# Simplified interface

def run(statement, globals=None, locals=None):
 """Execute the *statement* (given as a string or a code object)
 under debugger control.

 The debugger prompt appears before any code is executed; you can set
 breakpoints and type continue, or you can step through the statement
 using step or next.

 The optional *globals* and *locals* arguments specify the
 environment in which the code is executed; by default the
 dictionary of the module __main__ is used (see the explanation of
 the built-in exec() or eval() functions.).
 """
 Pdb().run(statement, globals, locals)

def runeval(expression, globals=None, locals=None):
 """Evaluate the *expression* (given as a string or a code object)
 under debugger control.

 When runeval() returns, it returns the value of the expression.
 Otherwise this function is similar to run().
 """
 return Pdb().runeval(expression, globals, locals)

def runctx(statement, globals, locals):
 # B/W compatibility
 run(statement, globals, locals)

def runcall(*args, **kwds):
 """Call the function (a function or method object, not a string)
 with the given arguments.

 When runcall() returns, it returns whatever the function call
 returned. The debugger prompt appears as soon as the function is
 entered.
 """
 return Pdb().runcall(*args, **kwds)

def set_trace(*, header=None, commands=None):
 """Enter the debugger at the calling stack frame.

 This is useful to hard-code a breakpoint at a given point in a
 program, even if the code is not otherwise being debugged (e.g. when
 an assertion fails). If given, *header* is printed to the console
 just before debugging begins. *commands* is an optional list of
 pdb commands to run when the debugger starts.
 """
 if Pdb._last_pdb_instance is not None:
 pdb = Pdb._last_pdb_instance
 else:
 pdb = Pdb(mode='inline', backend='monitoring', colorize=True)
 if header is not None:
 pdb.message(header)
 pdb.set_trace(sys._getframe().f_back, commands=commands)

async def set_trace_async(*, header=None, commands=None):
 """Enter the debugger at the calling stack frame, but in async mode.

 This should be used as await pdb.set_trace_async(). Users can do await
 if they enter the debugger with this function. Otherwise it's the same
 as set_trace().
 """
 if Pdb._last_pdb_instance is not None:
 pdb = Pdb._last_pdb_instance
 else:
 pdb = Pdb(mode='inline', backend='monitoring', colorize=True)
 if header is not None:
 pdb.message(header)
 await pdb.set_trace_async(sys._getframe().f_back, commands=commands)

# Remote PDB

class _PdbServer(Pdb):
 def __init__(
 self,
 sockfile,
 signal_server=None,
 owns_sockfile=True,
 colorize=False,
 **kwargs,
 ):
 self._owns_sockfile = owns_sockfile
 self._interact_state = None
 self._sockfile = sockfile
 self._command_name_cache = []
 self._write_failed = False
 if signal_server:
 # Only started by the top level _PdbServer, not recursive ones.
 self._start_signal_listener(signal_server)
 # Override the `colorize` attribute set by the parent constructor,
 # because it checks the server's stdout, rather than the client's.
 super().__init__(colorize=False, **kwargs)
 self.colorize = colorize

 @staticmethod
 def protocol_version():
 # By default, assume a client and server are compatible if they run
 # the same Python major.minor version. We'll try to keep backwards
 # compatibility between patch versions of a minor version if possible.
 # If we do need to change the protocol in a patch version, we'll change
 # `revision` to the patch version where the protocol changed.
 # We can ignore compatibility for pre-release versions; sys.remote_exec
 # can't attach to a pre-release version except from that same version.
 v = sys.version_info
 revision = 0
 return int(f"{v.major:02X}{v.minor:02X}{revision:02X}F0", 16)

 def _ensure_valid_message(self, msg):
 # Ensure the message conforms to our protocol.
 # If anything needs to be changed here for a patch release of Python,
 # the 'revision' in protocol_version() should be updated.
 match msg:
 case {"message": str(), "type": str()}:
 # Have the client show a message. The client chooses how to
 # format the message based on its type. The currently defined
 # types are "info" and "error". If a message has a type the
 # client doesn't recognize, it must be treated as "info".
 pass
 case {"help": str()}:
 # Have the client show the help for a given argument.
 pass
 case {"prompt": str(), "state": str()}:
 # Have the client display the given prompt and wait for a reply
 # from the user. If the client recognizes the state it may
 # enable mode-specific features like multi-line editing.
 # If it doesn't recognize the state it must prompt for a single
 # line only and send it directly to the server. A server won't
 # progress until it gets a "reply" or "signal" message, but can
 # process "complete" requests while waiting for the reply.
 pass
 case {
 "completions": list(completions)
 } if all(isinstance(c, str) for c in completions):
 # Return valid completions for a client's "complete" request.
 pass
 case {
 "command_list": list(command_list)
 } if all(isinstance(c, str) for c in command_list):
 # Report the list of legal PDB commands to the client.
 # Due to aliases this list is not static, but the client
 # needs to know it for multi-line editing.
 pass
 case _:
 raise AssertionError(
 f"PDB message doesn't follow the schema! {msg}"
 )

 @classmethod
 def _start_signal_listener(cls, address):
 def listener(sock):
 with closing(sock):
 # Check if the interpreter is finalizing every quarter of a second.
 # Clean up and exit if so.
 sock.settimeout(0.25)
 sock.shutdown(socket.SHUT_WR)
 while not shut_down.is_set():
 try:
 data = sock.recv(1024)
 except socket.timeout:
 continue
 if data == b"":
 return # EOF
 signal.raise_signal(signal.SIGINT)

 def stop_thread():
 shut_down.set()
 thread.join()

 # Use a daemon thread so that we don't detach until after all non-daemon
 # threads are done. Use an atexit handler to stop gracefully at that point,
 # so that our thread is stopped before the interpreter is torn down.
 shut_down = threading.Event()
 thread = threading.Thread(
 target=listener,
 args=[socket.create_connection(address, timeout=5)],
 daemon=True,
 )
 atexit.register(stop_thread)
 thread.start()

 def _send(self, **kwargs):
 self._ensure_valid_message(kwargs)
 json_payload = json.dumps(kwargs)
 try:
 self._sockfile.write(json_payload.encode() + b"\n")
 self._sockfile.flush()
 except (OSError, ValueError):
 # We get an OSError if the network connection has dropped, and a
 # ValueError if detach() if the sockfile has been closed. We'll
 # handle this the next time we try to read from the client instead
 # of trying to handle it from everywhere _send() may be called.
 # Track this with a flag rather than assuming readline() will ever
 # return an empty string because the socket may be half-closed.
 self._write_failed = True

 @typing.override
 def message(self, msg, end="\n"):
 self._send(message=str(msg) + end, type="info")

 @typing.override
 def error(self, msg):
 self._send(message=str(msg), type="error")

 def _get_input(self, prompt, state) -> str:
 # Before displaying a (Pdb) prompt, send the list of PDB commands
 # unless we've already sent an up-to-date list.
 if state == "pdb" and not self._command_name_cache:
 self._command_name_cache = self.completenames("", "", 0, 0)
 self._send(command_list=self._command_name_cache)
 self._send(prompt=prompt, state=state)
 return self._read_reply()

 def _read_reply(self):
 # Loop until we get a 'reply' or 'signal' from the client,
 # processing out-of-band 'complete' requests as they arrive.
 while True:
 if self._write_failed:
 raise EOFError

 msg = self._sockfile.readline()
 if not msg:
 raise EOFError

 try:
 payload = json.loads(msg)
 except json.JSONDecodeError:
 self.error(f"Disconnecting: client sent invalid JSON {msg!r}")
 raise EOFError

 match payload:
 case {"reply": str(reply)}:
 return reply
 case {"signal": str(signal)}:
 if signal == "INT":
 raise KeyboardInterrupt
 elif signal == "EOF":
 raise EOFError
 else:
 self.error(
 f"Received unrecognized signal: {signal}"
 )
 # Our best hope of recovering is to pretend we
 # got an EOF to exit whatever mode we're in.
 raise EOFError
 case {
 "complete": {
 "text": str(text),
 "line": str(line),
 "begidx": int(begidx),
 "endidx": int(endidx),
 }
 }:
 items = self._complete_any(text, line, begidx, endidx)
 self._send(completions=items)
 continue
 # Valid JSON, but doesn't meet the schema.
 self.error(f"Ignoring invalid message from client: {msg}")

 def _complete_any(self, text, line, begidx, endidx):
 # If we're in 'interact' mode, we need to use the default completer
 if self._interact_state:
 compfunc = self.completedefault
 else:
 if begidx == 0:
 return self.completenames(text, line, begidx, endidx)

 cmd = self.parseline(line)[0]
 if cmd:
 compfunc = getattr(self, "complete_" + cmd, self.completedefault)
 else:
 compfunc = self.completedefault
 return compfunc(text, line, begidx, endidx)

 def cmdloop(self, intro=None):
 self.preloop()
 if intro is not None:
 self.intro = intro
 if self.intro:
 self.message(str(self.intro))
 stop = None
 while not stop:
 if self._interact_state is not None:
 try:
 reply = self._get_input(prompt=">>> ", state="interact")
 except KeyboardInterrupt:
 # Match how KeyboardInterrupt is handled in a REPL
 self.message("\nKeyboardInterrupt")
 except EOFError:
 self.message("\n*exit from pdb interact command*")
 self._interact_state = None
 else:
 self._run_in_python_repl(reply)
 continue

 if not self.cmdqueue:
 try:
 state = "commands" if self.commands_defining else "pdb"
 reply = self._get_input(prompt=self.prompt, state=state)
 except EOFError:
 reply = "EOF"

 self.cmdqueue.append(reply)

 line = self.cmdqueue.pop(0)
 line = self.precmd(line)
 stop = self.onecmd(line)
 stop = self.postcmd(stop, line)
 self.postloop()

 def postloop(self):
 super().postloop()
 if self.quitting:
 self.detach()

 @contextmanager
 def _maybe_use_pyrepl_as_stdin(self):
 # The server reads every command from the client over the socket, never
 # from a local pyrepl. The base implementation swaps in pyrepl as stdin
 # and blanks `self.prompt` to '' (pyrepl would draw the prompt itself),
 # which here would transmit an empty prompt to the client whenever the
 # target process happens to be pyrepl-capable. Keep the real prompt.
 yield

 def detach(self):
 # Detach the debugger and close the socket without raising BdbQuit
 self.quitting = False
 if self._owns_sockfile:
 # Don't try to reuse this instance, it's not valid anymore.
 Pdb._last_pdb_instance = None
 try:
 self._sockfile.close()
 except OSError:
 # close() can fail if the connection was broken unexpectedly.
 pass

 def do_debug(self, arg):
 # Clear our cached list of valid commands; the recursive debugger might
 # send its own differing list, and so ours needs to be re-sent.
 self._command_name_cache = []
 return super().do_debug(arg)

 def do_alias(self, arg):
 # Clear our cached list of valid commands; one might be added.
 self._command_name_cache = []
 return super().do_alias(arg)

 def do_unalias(self, arg):
 # Clear our cached list of valid commands; one might be removed.
 self._command_name_cache = []
 return super().do_unalias(arg)

 def do_help(self, arg):
 # Tell the client to render the help, since it might need a pager.
 self._send(help=arg)

 do_h = do_help

 def _interact_displayhook(self, obj):
 # Like the default `sys.displayhook` except sending a socket message.
 if obj is not None:
 self.message(repr(obj))
 builtins._ = obj

 def _run_in_python_repl(self, lines):
 # Run one 'interact' mode code block against an existing namespace.
 assert self._interact_state
 save_displayhook = sys.displayhook
 try:
 sys.displayhook = self._interact_displayhook
 code_obj = self._interact_state["compiler"](lines + "\n")
 if code_obj is None:
 raise SyntaxError("Incomplete command")
 exec(code_obj, self._interact_state["ns"])
 except:
 self._error_exc()
 finally:
 sys.displayhook = save_displayhook

 def do_interact(self, arg):
 # Prepare to run 'interact' mode code blocks, and trigger the client
 # to start treating all input as Python commands, not PDB ones.
 self.message("*pdb interact start*")
 self._interact_state = dict(
 compiler=codeop.CommandCompiler(),
 ns={**self.curframe.f_globals, **self.curframe.f_locals},
 )

 @typing.override
 def _create_recursive_debugger(self):
 return _PdbServer(
 self._sockfile,
 owns_sockfile=False,
 colorize=self.colorize,
 )

 @typing.override
 def _prompt_for_confirmation(self, prompt, default):
 try:
 return self._get_input(prompt=prompt, state="confirm")
 except (EOFError, KeyboardInterrupt):
 return default

 def do_run(self, arg):
 self.error("remote PDB cannot restart the program")

 do_restart = do_run

 def _error_exc(self):
 if self._interact_state and isinstance(sys.exception(), SystemExit):
 # If we get a SystemExit in 'interact' mode, exit the REPL.
 self._interact_state = None
 ret = super()._error_exc()
 self.message("*exit from pdb interact command*")
 return ret
 else:
 return super()._error_exc()

 def default(self, line):
 # Unlike Pdb, don't prompt for more lines of a multi-line command.
 # The remote needs to send us the whole block in one go.
 try:
 candidate = line.removeprefix("!") + "\n"
 if codeop.compile_command(candidate, "<stdin>", "single") is None:
 raise SyntaxError("Incomplete command")
 return super().default(candidate)
 except:
 self._error_exc()


class _PdbClient:
 def __init__(self, pid, server_socket, interrupt_sock):
 self.pid = pid
 self.read_buf = b""
 self.signal_read = None
 self.signal_write = None
 self.sigint_received = False
 self.raise_on_sigint = False
 self.server_socket = server_socket
 self.interrupt_sock = interrupt_sock
 self.pdb_instance = Pdb()
 self.pdb_commands = set()
 self.completion_matches = []
 self.state = "dumb"
 self.write_failed = False
 self.multiline_block = False

 def _ensure_valid_message(self, msg):
 # Ensure the message conforms to our protocol.
 # If anything needs to be changed here for a patch release of Python,
 # the 'revision' in protocol_version() should be updated.
 match msg:
 case {"reply": str()}:
 # Send input typed by a user at a prompt to the remote PDB.
 pass
 case {"signal": "EOF"}:
 # Tell the remote PDB that the user pressed ^D at a prompt.
 pass
 case {"signal": "INT"}:
 # Tell the remote PDB that the user pressed ^C at a prompt.
 pass
 case {
 "complete": {
 "text": str(),
 "line": str(),
 "begidx": int(),
 "endidx": int(),
 }
 }:
 # Ask the remote PDB what completions are valid for the given
 # parameters, using readline's completion protocol.
 pass
 case _:
 raise AssertionError(
 f"PDB message doesn't follow the schema! {msg}"
 )

 def _send(self, **kwargs):
 self._ensure_valid_message(kwargs)
 json_payload = json.dumps(kwargs)
 try:
 self.server_socket.sendall(json_payload.encode() + b"\n")
 except OSError:
 # This means that the client has abruptly disconnected, but we'll
 # handle that the next time we try to read from the client instead
 # of trying to handle it from everywhere _send() may be called.
 # Track this with a flag rather than assuming readline() will ever
 # return an empty string because the socket may be half-closed.
 self.write_failed = True

 def _readline(self):
 if self.sigint_received:
 # There's a pending unhandled SIGINT. Handle it now.
 self.sigint_received = False
 raise KeyboardInterrupt

 # Wait for either a SIGINT or a line or EOF from the PDB server.
 selector = selectors.DefaultSelector()
 selector.register(self.signal_read, selectors.EVENT_READ)
 selector.register(self.server_socket, selectors.EVENT_READ)

 while b"\n" not in self.read_buf:
 for key, _ in selector.select():
 if key.fileobj == self.signal_read:
 self.signal_read.recv(1024)
 if self.sigint_received:
 # If not, we're reading wakeup events for sigints that
 # we've previously handled, and can ignore them.
 self.sigint_received = False
 raise KeyboardInterrupt
 elif key.fileobj == self.server_socket:
 data = self.server_socket.recv(16 * 1024)
 self.read_buf += data
 if not data and b"\n" not in self.read_buf:
 # EOF without a full final line. Drop the partial line.
 self.read_buf = b""
 return b""

 ret, sep, self.read_buf = self.read_buf.partition(b"\n")
 return ret + sep

 def read_input(self, prompt, multiline_block):
 self.multiline_block = multiline_block
 with self._sigint_raises_keyboard_interrupt():
 return input(prompt)

 def read_command(self, prompt):
 reply = self.read_input(prompt, multiline_block=False)
 if self.state == "dumb":
 # No logic applied whatsoever, just pass the raw reply back.
 return reply

 prefix = ""
 if self.state == "pdb":
 # PDB command entry mode
 cmd = self.pdb_instance.parseline(reply)[0]
 if cmd in self.pdb_commands or reply.strip() == "":
 # Recognized PDB command, or blank line repeating last command
 return reply

 # Otherwise, explicit or implicit exec command
 if reply.startswith("!"):
 prefix = "!"
 reply = reply.removeprefix(prefix).lstrip()

 if codeop.compile_command(reply + "\n", "<stdin>", "single") is not None:
 # Valid single-line statement
 return prefix + reply

 # Otherwise, valid first line of a multi-line statement
 more_prompt = "...".ljust(len(prompt))
 while codeop.compile_command(reply, "<stdin>", "single") is None:
 reply += "\n" + self.read_input(more_prompt, multiline_block=True)

 return prefix + reply

 @contextmanager
 def readline_completion(self, completer):
 try:
 import readline
 except ImportError:
 yield
 return

 old_completer = readline.get_completer()
 try:
 readline.set_completer(completer)
 if readline.backend == "editline":
 # libedit uses "^I" instead of "tab"
 command_string = "bind ^I rl_complete"
 else:
 command_string = "tab: complete"
 readline.parse_and_bind(command_string)
 yield
 finally:
 readline.set_completer(old_completer)

 @contextmanager
 def _sigint_handler(self):
 # Signal handling strategy:
 # - When we call input() we want a SIGINT to raise KeyboardInterrupt
 # - Otherwise we want to write to the wakeup FD and set a flag.
 # We'll break out of select() when the wakeup FD is written to,
 # and we'll check the flag whenever we're about to accept input.
 def handler(signum, frame):
 self.sigint_received = True
 if self.raise_on_sigint:
 # One-shot; don't raise again until the flag is set again.
 self.raise_on_sigint = False
 self.sigint_received = False
 raise KeyboardInterrupt

 sentinel = object()
 old_handler = sentinel
 old_wakeup_fd = sentinel

 self.signal_read, self.signal_write = socket.socketpair()
 with (closing(self.signal_read), closing(self.signal_write)):
 self.signal_read.setblocking(False)
 self.signal_write.setblocking(False)

 try:
 old_handler = signal.signal(signal.SIGINT, handler)

 try:
 old_wakeup_fd = signal.set_wakeup_fd(
 self.signal_write.fileno(),
 warn_on_full_buffer=False,
 )
 yield
 finally:
 # Restore the old wakeup fd if we installed a new one
 if old_wakeup_fd is not sentinel:
 signal.set_wakeup_fd(old_wakeup_fd)
 finally:
 self.signal_read = self.signal_write = None
 if old_handler is not sentinel:
 # Restore the old handler if we installed a new one
 signal.signal(signal.SIGINT, old_handler)

 @contextmanager
 def _sigint_raises_keyboard_interrupt(self):
 if self.sigint_received:
 # There's a pending unhandled SIGINT. Handle it now.
 self.sigint_received = False
 raise KeyboardInterrupt

 try:
 self.raise_on_sigint = True
 yield
 finally:
 self.raise_on_sigint = False

 def cmdloop(self):
 with (
 self._sigint_handler(),
 self.readline_completion(self.complete),
 ):
 while not self.write_failed:
 try:
 if not (payload_bytes := self._readline()):
 break
 except KeyboardInterrupt:
 self.send_interrupt()
 continue

 try:
 payload = json.loads(payload_bytes)
 except json.JSONDecodeError:
 print(
 f"*** Invalid JSON from remote: {payload_bytes!r}",
 flush=True,
 )
 continue

 self.process_payload(payload)

 def send_interrupt(self):
 if self.interrupt_sock is not None:
 # Write to a socket that the PDB server listens on. This triggers
 # the remote to raise a SIGINT for itself. We do this because
 # Windows doesn't allow triggering SIGINT remotely.
 # See https://stackoverflow.com/a/35792192 for many more details.
 self.interrupt_sock.sendall(signal.SIGINT.to_bytes())
 else:
 # On Unix we can just send a SIGINT to the remote process.
 # This is preferable to using the signal thread approach that we
 # use on Windows because it can interrupt IO in the main thread.
 os.kill(self.pid, signal.SIGINT)

 def process_payload(self, payload):
 match payload:
 case {
 "command_list": command_list
 } if all(isinstance(c, str) for c in command_list):
 self.pdb_commands = set(command_list)
 case {"message": str(msg), "type": str(msg_type)}:
 if msg_type == "error":
 print("***", msg, flush=True)
 else:
 print(msg, end="", flush=True)
 case {"help": str(arg)}:
 self.pdb_instance.do_help(arg)
 case {"prompt": str(prompt), "state": str(state)}:
 if state not in ("pdb", "interact"):
 state = "dumb"
 self.state = state
 self.prompt_for_reply(prompt)
 case _:
 raise RuntimeError(f"Unrecognized payload {payload}")

 def prompt_for_reply(self, prompt):
 while True:
 try:
 payload = {"reply": self.read_command(prompt)}
 except EOFError:
 payload = {"signal": "EOF"}
 except KeyboardInterrupt:
 payload = {"signal": "INT"}
 except Exception as exc:
 msg = traceback.format_exception_only(exc)[-1].strip()
 print("***", msg, flush=True)
 continue

 self._send(**payload)
 return

 def complete(self, text, state):
 import readline

 if state == 0:
 self.completion_matches = []
 if self.state not in ("pdb", "interact"):
 return None

 origline = readline.get_line_buffer()
 line = origline.lstrip()
 if self.multiline_block:
 # We're completing a line contained in a multi-line block.
 # Force the remote to treat it as a Python expression.
 line = "! " + line
 offset = len(origline) - len(line)
 begidx = readline.get_begidx() - offset
 endidx = readline.get_endidx() - offset

 msg = {
 "complete": {
 "text": text,
 "line": line,
 "begidx": begidx,
 "endidx": endidx,
 }
 }

 self._send(**msg)
 if self.write_failed:
 return None

 payload = self._readline()
 if not payload:
 return None

 payload = json.loads(payload)
 if "completions" not in payload:
 raise RuntimeError(
 f"Failed to get valid completions. Got: {payload}"
 )

 self.completion_matches = payload["completions"]
 try:
 return self.completion_matches[state]
 except IndexError:
 return None


def _connect(
 *,
 host,
 port,
 frame,
 commands,
 version,
 signal_raising_thread,
 colorize,
):
 with closing(socket.create_connection((host, port))) as conn:
 sockfile = conn.makefile("rwb")

 # The client requests this thread on Windows but not on Unix.
 # Most tests don't request this thread, to keep them simpler.
 if signal_raising_thread:
 signal_server = (host, port)
 else:
 signal_server = None

 remote_pdb = _PdbServer(
 sockfile,
 signal_server=signal_server,
 colorize=colorize,
 )
 weakref.finalize(remote_pdb, sockfile.close)

 if Pdb._last_pdb_instance is not None:
 remote_pdb.error("Another PDB instance is already attached.")
 elif version != remote_pdb.protocol_version():
 target_ver = f"0x{remote_pdb.protocol_version():08X}"
 attach_ver = f"0x{version:08X}"
 remote_pdb.error(
 f"The target process is running a Python version that is"
 f" incompatible with this PDB module."
 f"\nTarget process pdb protocol version: {target_ver}"
 f"\nLocal pdb module's protocol version: {attach_ver}"
 )
 else:
 remote_pdb.set_trace(frame=frame, commands=commands.splitlines())


def attach(pid, commands=()):
 """Attach to a running process with the given PID."""
 with ExitStack() as stack:
 server = stack.enter_context(
 closing(socket.create_server(("localhost", 0)))
 )
 port = server.getsockname()[1]

 connect_script = stack.enter_context(
 tempfile.NamedTemporaryFile("w", delete_on_close=False)
 )

 use_signal_thread = sys.platform == "win32"
 colorize = _colorize.can_colorize()

 connect_script.write(
 textwrap.dedent(
 f"""
 import pdb, sys
 pdb._connect(
 host="localhost",
 port={port},
 frame=sys._getframe(1),
 commands={json.dumps("\n".join(commands))},
 version={_PdbServer.protocol_version()},
 signal_raising_thread={use_signal_thread!r},
 colorize={colorize!r},
 )
 """
 )
 )
 connect_script.close()
 orig_mode = os.stat(connect_script.name).st_mode
 os.chmod(connect_script.name, orig_mode | stat.S_IROTH | stat.S_IRGRP)
 sys.remote_exec(pid, connect_script.name)

 # TODO Add a timeout? Or don't bother since the user can ^C?
 client_sock, _ = server.accept()
 stack.enter_context(closing(client_sock))

 if use_signal_thread:
 interrupt_sock, _ = server.accept()
 stack.enter_context(closing(interrupt_sock))
 interrupt_sock.setblocking(False)
 else:
 interrupt_sock = None

 _PdbClient(pid, client_sock, interrupt_sock).cmdloop()


# Post-Mortem interface

def post_mortem(t=None):
 """Enter post-mortem debugging of the given *traceback*, or *exception*
 object.

 If no traceback is given, it uses the one of the exception that is
 currently being handled (an exception must be being handled if the
 default is to be used).

 If `t` is an exception object, the `exceptions` command makes it possible to
 list and inspect its chained exceptions (if any).
 """
 return _post_mortem(t, Pdb())


def _post_mortem(t, pdb_instance):
 """
 Private version of post_mortem, which allow to pass a pdb instance
 for testing purposes.
 """
 # handling the default
 if t is None:
 exc = sys.exception()
 if exc is not None:
 t = exc.__traceback__

 if t is None or (isinstance(t, BaseException) and t.__traceback__ is None):
 raise ValueError("A valid traceback must be passed if no "
 "exception is being handled")

 pdb_instance.reset()
 pdb_instance.interaction(None, t)


def pm():
 """Enter post-mortem debugging of the traceback found in sys.last_exc."""
 post_mortem(sys.last_exc)


# Main program for testing

TESTCMD = 'import x; x.main()'

def test():
 run(TESTCMD)

# print help
def help():
 import pydoc
 pydoc.pager(__doc__)

_usage = """\
Debug the Python program given by `pyfile`. Alternatively,
an executable module or package to debug can be specified using
the `-m` switch. You can also attach to a running Python process
using the `-p` option with its PID.

Initial commands are read from `.pdbrc` files in your home directory
and in the current directory, if they exist. Commands supplied with
`-c` are executed after commands from `.pdbrc` files.

To let the script run until an exception occurs, use `-c continue`.
To let the script run up to a given line X in the debugged file, use
`-c 'until X'`."""


def exit_with_permission_help_text():
 """
 Prints a message pointing to platform-specific permission help text and exits the program.
 This function is called when a PermissionError is encountered while trying
 to attach to a process.
 """
 print(
 "Error: The specified process cannot be attached to due to insufficient permissions.\n"
 "See the Python documentation for details on required privileges and troubleshooting:\n"
 "https://docs.python.org/3.14/howto/remote_debugging.html#permission-requirements\n"
 )
 sys.exit(1)


def parse_args():
 # We want pdb to be as intuitive as possible to users, so we need to do some
 # heuristic parsing to deal with ambiguity.
 # For example:
 # "python -m pdb -m foo -p 1" should pass "-p 1" to "foo".
 # "python -m pdb foo.py -m bar" should pass "-m bar" to "foo.py".
 # "python -m pdb -m foo -m bar" should pass "-m bar" to "foo".
 # This require some customized parsing logic to find the actual debug target.

 import argparse

 parser = argparse.ArgumentParser(
 usage="%(prog)s [-h] [-c command] (-m module | -p pid | pyfile) [args ...]",
 description=_usage,
 formatter_class=argparse.RawDescriptionHelpFormatter,
 allow_abbrev=False,
 )

 # Get all the commands out first. For backwards compatibility, we allow
 # -c commands to be after the target.
 parser.add_argument('-c', '--command', action='append', default=[], metavar='command', dest='commands',
 help='pdb commands to execute as if given in a `.pdbrc` file')

 opts, args = parser.parse_known_args()

 if not args:
 # If no arguments were given (python -m pdb), print the whole help message.
 # Without this check, argparse would only complain about missing required arguments.
 # We need to add the arguments definitions here to get a proper help message.
 parser.add_argument('-m', metavar='module', dest='module')
 parser.add_argument('-p', '--pid', type=int, help="attach to the specified PID", default=None)
 parser.print_help()
 sys.exit(2)
 elif args[0] == '-p' or args[0] == '--pid':
 # Attach to a pid
 parser.add_argument('-p', '--pid', type=int, help="attach to the specified PID", default=None)
 opts, args = parser.parse_known_args()
 if args:
 # For --pid, any extra arguments are invalid.
 parser.error(f"unrecognized arguments: {' '.join(args)}")
 elif args[0] == '-m':
 # Debug a module, we only need the first -m module argument.
 # The rest is passed to the module itself.
 parser.add_argument('-m', metavar='module', dest='module')
 opt_module = parser.parse_args(args[:2])
 opts.module = opt_module.module
 args = args[2:]
 elif args[0] == '--':
 args.pop(0)
 if not args:
 parser.error("missing script or module to run")
 elif args[0].startswith('-'):
 # Invalid argument before the script name.
 invalid_args = list(itertools.takewhile(lambda a: a.startswith('-'), args))
 parser.error(f"unrecognized arguments: {' '.join(invalid_args)}")

 # Otherwise it's debugging a script and we already parsed all -c commands.

 return opts, args

def main():
 opts, args = parse_args()

 if getattr(opts, 'pid', None) is not None:
 try:
 attach(opts.pid, opts.commands)
 except RuntimeError:
 print(
 f"Cannot attach to pid {opts.pid}, please make sure that the process exists "
 "and is using the same Python version."
 )
 sys.exit(1)
 except PermissionError:
 exit_with_permission_help_text()
 return
 elif getattr(opts, 'module', None) is not None:
 file = opts.module
 target = _ModuleTarget(file)
 else:
 file = args.pop(0)
 if file.endswith('.pyz'):
 target = _ZipTarget(file)
 else:
 target = _ScriptTarget(file)

 sys.argv[:] = [file] + args # Hide "pdb.py" and pdb options from argument list

 # Note on saving/restoring sys.argv: it's a good idea when sys.argv was
 # modified by the script being debugged. It's a bad idea when it was
 # changed by the user from the command line. There is a "restart" command
 # which allows explicit specification of command line arguments.
 pdb = Pdb(mode='cli', backend='monitoring', colorize=True)
 pdb.rcLines.extend(opts.commands)
 while True:
 try:
 pdb._run(target)
 except Restart:
 print("Restarting", target, "with arguments:")
 print("\t" + " ".join(sys.argv[1:]))
 except SystemExit as e:
 # In most cases SystemExit does not warrant a post-mortem session.
 print("The program exited via sys.exit(). Exit status:", end=' ')
 print(e)
 except BaseException as e:
 traceback.print_exception(e, colorize=_colorize.can_colorize())
 print("Uncaught exception. Entering post mortem debugging")
 print("Running 'cont' or 'step' will restart the program")
 try:
 pdb.interaction(None, e)
 except Restart:
 print("Restarting", target, "with arguments:")
 print("\t" + " ".join(sys.argv[1:]))
 continue
 if pdb._user_requested_quit:
 break
 print("The program finished and will be restarted")


# When invoked as main program, invoke the debugger on a script
if __name__ == '__main__':
 import pdb
 pdb.main()