Embedding: TypeError: signal handler must be signal.SIG_IGN, signal.SIG_DFL, or a callable object

[juju4]

Bug report

Bug description:

When using PEP 578 and 551 entry points to log python activity on Fedora-41, it results in above error.
setting TERM=dumb is a valid workaround

build ok (tested on Fedora 41/python 3.13.2)
usage nok (TypeError, see readme.md)

$ ./spython
Python 3.13.2 (main, Feb  4 2025, 00:00:00) [GCC 14.2.1 20250110 (Red Hat 14.2.1-7)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> print("hello")
Traceback (most recent call last):
  File "<frozen runpy>", line 198, in _run_module_as_main
  File "<frozen runpy>", line 88, in _run_code
  File "/usr/lib64/python3.13/_pyrepl/__main__.py", line 6, in <module>
    __pyrepl_interactive_console()
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^
  File "/usr/lib64/python3.13/_pyrepl/main.py", line 59, in interactive_console
    run_multiline_interactive_console(console)
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^
  File "/usr/lib64/python3.13/_pyrepl/simple_interact.py", line 143, in run_multiline_interactive_console
    statement = multiline_input(more_lines, ps1, ps2)
  File "/usr/lib64/python3.13/_pyrepl/readline.py", line 389, in multiline_input
    return reader.readline()
           ~~~~~~~~~~~~~~~^^
  File "/usr/lib64/python3.13/_pyrepl/reader.py", line 806, in readline
    self.restore()
    ~~~~~~~~~~~~^^
  File "/usr/lib64/python3.13/_pyrepl/reader.py", line 659, in restore
    self.console.restore()
    ~~~~~~~~~~~~~~~~~~~~^^
  File "/usr/lib64/python3.13/_pyrepl/unix_console.py", line 380, in restore
    signal.signal(signal.SIGWINCH, self.old_sigwinch)
    ~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib64/python3.13/signal.py", line 58, in signal
    handler = _signal.signal(_enum_to_int(signalnum), _enum_to_int(handler))
TypeError: signal handler must be signal.SIG_IGN, signal.SIG_DFL, or a callable object

Follow-up of
https://github.com/juju4/spython/tree/devel-journald/journald (code)
zooba/spython#13

CPython versions tested on:

3.13

Operating systems tested on:

Linux

[StanFromIreland]

PEPs are not documentation. Please try again using the docs and see if the error still occurs.

[picnixz]

I don't know if the issue is the user code or not but it might be a weird interaction with the new REPL.

[ZeroIntensity]

At a super quick glance, this looks like it could be caused by random UAF silliness in pymalloc. This Py_DECREF in your code doesn't look right:

https://github.com/juju4/spython/blob/1c6a4627158072228ef2212c7f5821fe6088f230/journald/spython.c#L42

References stored by PyArg_ParseTuple aren't strong!

[juju4]

Code was adapted to journald from the syslog example.
For Py_DECREF, should it be paired with a Py_INCREF or can be used on its own? commenting it, does not help with initial bug.
On PyArg_ParseTuple, is there an alternative?
As said in initial issue, using TERM screen-256color and xterm, or with PYTHONUSEREPL=0 does not help. but TERM=dumb works.
The pointed docs does not help me to implement the wanted activity logging/auditing. That's where zooba example is helpful and did not find similar resources.
journald logs end with

spython[1078515]: detected unhandled Python exception in 'interactive mode'

[ZeroIntensity]

For Py_DECREF, should it be paired with a Py_INCREF or can be used on its own? commenting it, does not help with initial bug.

I'm not sure what you mean. If you own a strong reference, then you need to Py_DECREF it, or hand it off to something that will ("stealing a reference"). PyArg_ParseTuple acquires borrowed references, so you aren't supposed to Py_DECREF them.

Anyways, this seems unrelated to audit hooks. The following is a sufficient repro:

#include <Python.h>

int
main(int argc, char **argv)
{
    PyConfig config;

    PyConfig_InitIsolatedConfig(&config);
    Py_InitializeFromConfig(&config);

    return Py_RunMain();
}

[ZeroIntensity]

My theory right now is that you can't use the signal module in an isolated Python runtime, but the new REPL uses signal by default. cc @pablogsal as a REPL expert.