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1. plashchynski

   added

   type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

   on Mar 13, 2025
2. StanFromIreland commented on Mar 13, 2025

   

   StanFromIreland

   on Mar 13, 2025

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   Yes, its listed as a dependency. Behavior like this is to be expected. I don't really see a need for anything to be introduced (eg warnings).
3. plashchynski commented on Mar 13, 2025

   

   plashchynski

   on Mar 13, 2025

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   After a quick exploration, I've found that the warning caused by an ImportError exception in the following code in pyrepl:

   cpython/Lib/_pyrepl/readline.py

   Lines 45 to 48 in e9d210b

   	try:
   	from .unix_console import UnixConsole as Console, _error
   	except ImportError:
   	from .windows_console import WindowsConsole as Console, _error

   It's unable to load unix_console because of lack of libffi-dev (and _ctypes) package cause the following import error:

     File "/home/dzmitry/cpython/Lib/_pyrepl/readline.py", line 46, in <module>
       from .unix_console import UnixConsole as Console, _error
     File "/home/dzmitry/cpython/Lib/_pyrepl/unix_console.py", line 35, in <module>
       from . import curses
     File "/home/dzmitry/cpython/Lib/_pyrepl/curses.py", line 28, in <module>
       from . import _minimal_curses as _curses  # type: ignore[no-redef]
       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
     File "/home/dzmitry/cpython/Lib/_pyrepl/_minimal_curses.py", line 12, in <module>
       import ctypes
     File "/home/dzmitry/cpython/Lib/ctypes/__init__.py", line 8, in <module>
       from _ctypes import Union, Structure, Array
   ModuleNotFoundError: No module named '_ctypes'
   

   So it fallbacks to import of windows_console on Linux, resulting in another ModuleNotFoundError that results in the No module named 'msvcrt' warning.

   In such situation, I'd expect to see a warning about lack of _ctypes. So, may we have here some platform checks instead of catching and suppressing import errors?

   cpython/Lib/_pyrepl/readline.py

   Lines 45 to 48 in e9d210b

   	try:
   	from .unix_console import UnixConsole as Console, _error
   	except ImportError:
   	from .windows_console import WindowsConsole as Console, _error
4. picnixz commented on Mar 13, 2025

   

   picnixz

   on Mar 13, 2025

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   We should warn at the make step or the configure step when libffi is not available I think.

   👍React with 👍1Reacted by Dzmitry Plashchynski
5. picnixz

   added

   extension-modulesC modules in the Modules dirC modules in the Modules dir

   buildThe build process and cross-buildThe build process and cross-build

   topic-ctypes

   on Mar 13, 2025
6. picnixz commented on Mar 13, 2025

   

   picnixz

   on Mar 13, 2025

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   cc @encukou WDYT is the best approach? (and how do we actually check it?) I'm actually surprised that make correctly worked here (aren't we checking the necessary dependencies?)
7. encukou commented on Mar 13, 2025

   

   encukou

   on Mar 13, 2025

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   ctypes is optional; libffi is not a build requirement.
   I'm not sure anyone knows what “optional” means exactly; see the zlib discussion.
8. picnixz commented on Mar 13, 2025

   

   picnixz

   on Mar 13, 2025

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   Maybe we should warn once we're done with make? like, if ctypes is not available and we're on Linux, then the new REPL won't work (maybe the old REPL could work?) Having a simple warning: can't use pyrepl: No module named 'msvcrt' doesn't really help in this case.

   👍React with 👍1Reacted by Dzmitry Plashchynski
9. picnixz

   added

   stdlibStandard Library Python modules in the Lib/ directoryStandard Library Python modules in the Lib/ directory

   topic-replRelated to the interactive shellRelated to the interactive shell

   3.13only security fixesonly security fixes

   and removed

   topic-ctypes

   extension-modulesC modules in the Modules dirC modules in the Modules dir

   on Mar 13, 2025
10. 25 remaining items

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11. miss-islington

    added a commit that references this issue on Jul 15, 2025

    pythongh-131189: Fix "msvcrt" import warning on Linux when "_ctypes" …

    ...

    36da690
12. ambv

    added a commit that references this issue on Jul 15, 2025

    [3.14] gh-131189: Fix "msvcrt" import warning on Linux when "_ctypes"…

    ...

    1154773
13. taegyunkim

    added a commit that references this issue on Aug 4, 2025

    pythongh-131189: Fix "msvcrt" import warning on Linux when "_ctypes" …

    ...

    0b768b1
14. jkfields commented on Aug 4, 2025

    

    jkfields

    on Aug 4, 2025

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    Bug report

    Bug description:

    Compilation on Ubuntu 24.04.2 with ./configure --with-pydebug without libffi-dev package installed cause the following unexpected warning while loading the resulting executable as ./python:

    warning: can't use pyrepl: No module named 'msvcrt'

    After installation of libffi-dev and recompilation the warning was resolved.

    CPython versions tested on:

    CPython main branch

    Operating systems tested on:

    Linux

    Linked PRs

    • gh-131189: Fix "msvcrt" import warning on Linux when "_ctypes" is not available. #131201
    • [3.14] gh-131189: Fix "msvcrt" import warning on Linux when "_ctypes" is not available. (GH-131201) #136668

    Related

    • pyrepl: restructure imports to give a meaningful error when curses is missing on POSIX #130046

    I received the same message with Python 3.13.5 on RHEL 9! I had to install ncurses-devel and readline-devel to make it go away.
15. skirpichev commented on Aug 5, 2025

    

    skirpichev

    on Aug 5, 2025

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    #131201 is not backported to 3.13.

    If this is intentional, then the bugreport might be closed. @ambv?
16. Agent-Hellboy

    added a commit that references this issue on Aug 19, 2025

    pythongh-131189: Fix "msvcrt" import warning on Linux when "_ctypes" …

    ...

    fa47647
17. chris-eibl commented on Aug 24, 2025

    

    chris-eibl

    on Aug 24, 2025

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    If possible, it would be nice to be backported since this frequently pops up (just recently https://discuss.python.org/t/cant-use-pyrepl-no-module-named-msvcrt-in-linux/67037/9). IDK whether #131201 qualifies for backport, though, but looks quite simple if that helps backporting :)
18. kumaraditya303

    added a commit that references this issue on Sep 9, 2025

    [3.14] pythongh-131189: Fix "msvcrt" import warning on Linux when "_c…

    ...

    bf2e1f0
19. ambv commented on Sep 15, 2025

    

    ambv

    on Sep 15, 2025

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    We can't backport this to 3.13, too much of a code difference between the branches and treating this as a bug fix is a stretch (that we used for 3.14, but that's before the final release).
20. ambv

    closed this as completedon Sep 15, 2025
21. miss-islington

    added a commit that references this issue on Sep 15, 2025

    pythongh-131189: Fix "msvcrt" import warning on Linux when "_ctypes" …

    ...

    a908ac6
22. ambv

    added a commit that references this issue on Sep 15, 2025

    [3.13] gh-131189: Fix "msvcrt" import warning on Linux when "_ctypes"…

    ...

    7452e95
23. picnixz

    added a commit that references this issue on Oct 13, 2025

    gh-131189: Remove `curses` mention from `PYTHON_BASIC_REPL` docs (#14…

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    0344db8
24. miss-islington

    added a commit that references this issue on Oct 13, 2025

    pythongh-131189: Remove `curses` mention from `PYTHON_BASIC_REPL` docs (

    ...

    360b664
25. picnixz

    added a commit that references this issue on Oct 13, 2025

    [3.14] gh-131189: Remove `curses` mention from `PYTHON_BASIC_REPL` do…

    ...

    0b84334