`while True: input()` produces a `lost sys.stderr` on `termux`

[mahdoosh1]

Bug report

Bug description:

~/huh $ python -c "while True: input()"
^Cobject address  : 0x6fb5d862c0
object refcount : 3
object type     : 0x724a070bd8
object type name: EOFError
object repr     : EOFError()
lost sys.stderr
~/huh $ python --version
Python 3.12.11

CPython versions tested on:

3.12 (from termux pkg)

Operating systems tested on:

Linux (Termux)

[zware]

I'm afraid you're going to have to be rather clearer about what exactly you're reporting here. There are a small handful of cases where fprintf(stderr, "lost sys.stderr\n"); is the expected result.

[ZeroIntensity]

I couldn't reproduce this on Linux:

$ python3.12 -c "while True: input()"
^CTraceback (most recent call last):
  File "<string>", line 1, in <module>
KeyboardInterrupt
$ python3.13 -c "while True: input()"
^CTraceback (most recent call last):
  File "<string>", line 1, in <module>
    while True: input()
                ~~~~~^^
KeyboardInterrupt

Are you running this inside of some fancy environment that breaks stderr?

[terryjreedy]

What's odd is that input() does not use stderr. It still works after sys.stderr = None.

[mahdoosh1]

Are you running this inside of some fancy environment that breaks stderr?

i don't really know, from what i see, keyboard interrupt isn't triggered until pressing Ctrl + D or enter (or other special keybinds i don't know)

i don't have the same issue in other programs so i suspect it's a python problem
the problem might be for Termux implementation if it's different, but i'm unsure
i'm not able to test at the time but one could compile cpython for termux and test it

also, did you try running it in interactive mode?

[ZeroIntensity]

Something seems screwed up with your file streams, so it's probably not a CPython problem. input is trying to raise an EOFError (presumably because there's no stdin?), and then Python fails while trying to send that to sys.stderr. A few questions:

1. What system are you on?
2. Does this happen with Python 3.13 or higher? 3.12 is security-only, so if there is a bug specific to <=3.12, we can't do much to fix it.
3. What shell are you using? (For example, bash -- Termux is a terminal emulator.)
4. Do you have any dependencies installed? It's possible something is running a pth file that's clobbering sys.

[picnixz]

This could happen when calling PyErr_Display() (which I believe it is the case since we are likely branching into the _PyObject_Dump(exc):

    if (PySys_GetOptionalAttr(&_Py_ID(stderr), &file) < 0) {
        PyObject *exc = PyErr_GetRaisedException();
        _PyObject_Dump(value);
        fprintf(stderr, "lost sys.stderr\n");
        _PyObject_Dump(exc);
        Py_DECREF(exc);
        return;
    }
    if (file == NULL) {
        _PyObject_Dump(value);
        fprintf(stderr, "lost sys.stderr\n");
        return;
    }

Another possibility of "lost sys.stderr" is when we're failing to print recursive exceptions. Anyway, I don't think it's a CPython issue, because "lost sys.stderr" usually happens when someone messed up with sys.stderr (it could also have been gone if sys finalized before I guess?)

[mahdoosh1]

we are likely branching into the _PyObject_Dump(exc):

    if (PySys_GetOptionalAttr(&_Py_ID(stderr), &file) < 0) {
        PyObject *exc = PyErr_GetRaisedException();
        _PyObject_Dump(value);
        fprintf(stderr, "lost sys.stderr\n");
        _PyObject_Dump(exc);
        Py_DECREF(exc);
        return;
    }
    if (file == NULL) {
        _PyObject_Dump(value);
        fprintf(stderr, "lost sys.stderr\n");
        return;
    }

in my logs there is no dump after "lost sys.stderr", why do you believe that's where we are branching?

[mahdoosh1]

1. What system are you on?

Redmi 12 (fire-global) HyperOS 2.0.204.0
Termux 0.118.0

2. Does this happen with Python 3.13 or higher? 3.12 is security-only, so if there is a bug specific to <=3.12, we can't do much to fix it.

python 3.13 or higher are unavailable in termux,
i tried this and here is the result:

~/.../shared/Download $ python3.13 -c 'while True: print(input())'
^CTraceback (most recent call last):
  File "<string>", line 1, in <module>
EOFError

it appears fixed

3. What shell are you using? (For example, bash -- Termux is a terminal emulator.)

GNU bash, version 5.3.0(1)-release (aarch64-unknown-linux-android)

4. Do you have any dependencies installed? It's possible something is running a pth file that's clobbering sys.
   i'm unsure what you're reffering to by "dependencies"

[picnixz]

in my logs there is no dump after "lost sys.stderr", why do you believe that's where we are branching?

Sorry I meant _PyObject_Dump(value). So that means that stderr is NULL (that is, it doesn't exist anymore). It could be a finalization issue or something else. Since the only "python3.13" for Termux seems ok, I'm going to close this as "wont fix" as 3.12 is security-only.

If you ever encounter this again once termux has some official Python 3.13, feel free to comment on this issue.