code.InteractiveConsole can crash if sys.excepthook is broken

[cfbolz]

BPO	43154
Nosy	@terryjreedy, @vstinner, @cfbolz, @Julian
Files	crash.log

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2021-02-07.16:26:30.537>
labels = ['type-bug', '3.10']
title = 'code.InteractiveConsole can crash if sys.excepthook is broken'
updated_at = <Date 2021-04-02.22:33:56.780>
user = 'https://github.com/cfbolz'

bugs.python.org fields:

activity = <Date 2021-04-02.22:33:56.780>
actor = 'terry.reedy'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = []
creation = <Date 2021-02-07.16:26:30.537>
creator = 'Carl.Friedrich.Bolz'
dependencies = []
files = ['49797']
hgrepos = []
issue_num = 43154
keywords = []
message_count = 3.0
messages = ['386593', '386892', '390108']
nosy_count = 4.0
nosy_names = ['terry.reedy', 'vstinner', 'Carl.Friedrich.Bolz', 'Julian']
pr_nums = []
priority = 'normal'
resolution = None
stage = 'test needed'
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue43154'
versions = ['Python 3.10']

Linked PRs

• gh-87320: dont crash in code module with bad sys.excepthook #122456
• [3.13] gh-87320: In the code module, handle exceptions raised in sys.excepthook (GH-122456) #122514
• [3.12] gh-87320: In the code module, handle exceptions raised in sys.excepthook (GH-122456) #122515

[cfbolz]

When using code.InteractiveConsole to implement a Python shell (like PyPy is doing), having a broken sys.excepthook set can crash the console (see attached terminal log). Instead, it should catch errors and report then ignore them (using sys.unraisablehook I would think, but right now it's not that simple to call unraisablehook from python code).

Related to https://bugs.python.org/issue43148

[terryjreedy]

unraiseable hook is not needed. The REPL does:

>>> sys.excepthook = lambda: None
>>> 1/0
Error in sys.excepthook:
TypeError: <lambda>() takes 0 positional arguments but 3 were given

Original exception was:
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ZeroDivisionError: division by zero
>>> (no crash)

---

code.Console in the REPL currently does:

>>> import sys
>>> sys.excepthook = 1
>>> arsdfsd
Error in sys.excepthook:
TypeError: 'int' object is not callable

Original exception was:
Traceback (most recent call last):
  File "F:\dev\3x\lib\code.py", line 90, in runcode
    exec(code, self.locals)
  File "<console>", line 1, in <module>
NameError: name 'arsdfsd' is not defined

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "F:\dev\3x\lib\code.py", line 301, in interact
    console.interact(banner, exitmsg)
  File "F:\dev\3x\lib\code.py", line 232, in interact
    more = self.push(line)
  File "F:\dev\3x\lib\code.py", line 258, in push
    more = self.runsource(source, self.filename)
  File "F:\dev\3x\lib\code.py", line 74, in runsource
    self.runcode(code)
  File "F:\dev\3x\lib\code.py", line 94, in runcode
    self.showtraceback()
  File "F:\dev\3x\lib\code.py", line 148, in showtraceback
    sys.excepthook(ei[0], ei[1], last_tb)
TypeError: 'int' object is not callable
>>> (code console crashes, evidenced by 'sys' not recognized

---

IDLE in its normal 2-process mode, since 3 weeks ago, does:

>>> sys.excepthook = lambda: None
>>> 1/0
Traceback (most recent call last):
  File "<pyshell#3>", line 1, in <module>
    1/0
ZeroDivisionError: division by zero

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "C:\Programs\Python310\lib\idlelib\run.py", line 576, in runcode
    sys.excepthook(*self.user_exc_info)
TypeError: <lambda>() takes 0 positional arguments but 3 were given
>>> (no crash)

In IDLE's 1-process mode, selected with -n command line option, the hook exception has several IDLE specific lines added, as with the code exception.  A return or two is needed to get >>> back.

---

In any case, both the immediate code exception and the defective hook exception are printed. The recent patch to IDLE, PR-24302, was to replace 'print_exception()' (ignoring excepthook) with

            if sys.excepthook is sys.__excepthook__:
                print_exception()
            else:
                try:
                    sys.excepthook(*self.user_exc_info)
                except:
                    print_exception()

I suggest that the code line 148, call to sys.excepthook be wrapped similarly (adjusted to write the lines if sys.excepthook fails).

IDLE's exception order is determine by the default context annotation. I don't know what the REPL does to change the output, but I prefer the default. I will prepare a PR.

code tests are in test.test_code_module because test_code tests code objects.

[terryjreedy]

code.InteractiveInterpreter handles SyntaxErrors separately in showsyntaxerror rather than showtraceback. The same problem arises with a bad excepthook in line 129.

[cfbolz]

This issue is a little bit more pressing now with pyrepl, because that is based on the code module. Here's Python 3.12:

Python 3.12.0 (main, Apr 28 2024, 22:42:26) [GCC 13.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys; sys.excepthook = object(); asdf
Error in sys.excepthook:
TypeError: 'object' object is not callable

Original exception was:
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'asdf' is not defined

And Python 3.13 (I tried on current 3.13 branch, 10cf7d6):

>>> import sys; sys.excepthook = object(); asdf
Error in sys.excepthook:
TypeError: 'object' object is not callable

Original exception was:
Traceback (most recent call last):
  File "/home/cfbolz/projects/cpython/Lib/code.py", line 91, in runcode
    exec(code, self.locals)
    ~~~~^^^^^^^^^^^^^^^^^^^
  File "<python-input-0>", line 1, in <module>
    import sys; sys.excepthook = object(); asdf
                                           ^^^^
NameError: name 'asdf' is not defined

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<frozen runpy>", line 198, in _run_module_as_main
  File "<frozen runpy>", line 88, in _run_code
  File "/home/cfbolz/projects/cpython/Lib/_pyrepl/__main__.py", line 6, in <module>
    __pyrepl_interactive_console()
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^
  File "/home/cfbolz/projects/cpython/Lib/_pyrepl/main.py", line 59, in interactive_console
    run_multiline_interactive_console(console)
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^
  File "/home/cfbolz/projects/cpython/Lib/_pyrepl/simple_interact.py", line 156, in run_multiline_interactive_console
    more = console.push(_strip_final_indent(statement), filename=input_name, _symbol="single")  # type: ignore[call-arg]
  File "/home/cfbolz/projects/cpython/Lib/code.py", line 303, in push
    more = self.runsource(source, filename, symbol=_symbol)
  File "/home/cfbolz/projects/cpython/Lib/_pyrepl/console.py", line 200, in runsource
    self.runcode(code)
    ~~~~~~~~~~~~^^^^^^
  File "/home/cfbolz/projects/cpython/Lib/code.py", line 95, in runcode
    self.showtraceback()
    ~~~~~~~~~~~~~~~~~~^^
  File "/home/cfbolz/projects/cpython/Lib/_pyrepl/console.py", line 168, in showtraceback
    super().showtraceback(colorize=self.can_colorize)
    ~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/cfbolz/projects/cpython/Lib/code.py", line 153, in showtraceback
    sys.excepthook(ei[0], ei[1], last_tb)
    ~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^
TypeError: 'object' object is not callable