Overriding SIGINT doesn't work as expected in the new REPL

[pablogsal]

Bug report

In the old REPL, overriding SIGINT and pressing Ctrl-C works as expected:

❯ python
Python 3.11.6 (main, Nov  3 2023, 17:05:41) [Clang 15.0.0 (clang-1500.0.40.1)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import signal
>>> signal.signal(signal.SIGINT, lambda *x: print("NOOOO"))
<built-in function default_int_handler>
>>> NOOOO
NOOOO

but in the new REPL it doesn't trigger the signal handler:

❯ ./python.exe
Python 3.14.0a0 (heads/more_offsets-dirty:9403c2cf58, Jun  6 2024, 12:10:11) [Clang 15.0.0 (clang-1500.3.9.4)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import signal
>>> signal.signal(signal.SIGINT, lambda *x: print("NOOOO"))
<built-in function default_int_handler>
>>>
KeyboardInterrupt
>>>

Linked PRs

• gh-120221: Deliver real singals on Ctrl-C and Ctrl-Z in the new REPL #120354
• [3.13] gh-120221: Deliver real singals on Ctrl-C and Ctrl-Z in the new REPL (GH-120354) #120368
• gh-120221: Support KeyboardInterrupt in asyncio REPL #123795
• [3.13] gh-120221: Support KeyboardInterrupt in asyncio REPL (GH-123795) #123799

[pablogsal]

CC: @lysnikolaou @ambv

[pablogsal]

This will be fixed by #120234

[vstinner]

I noticed the problem when trying to debug Python in gdb. CTRL+C doesn't go into gdb anymore. For now, I'm using a bash alias:

alias gdb='PYTHON_BASIC_REPL=1 gdb'

[vstinner]

Thank you. CTRL+C is gdb stops again the process as expected :)

[eryksun]

This could have been addressed by changing default_keymap in "Lib/_pyepl/reader.py" to map (r"\x03", "interrupt") instead of mapping it to the ctrl_c command. The interrupt command calls os.kill(os.getpid(), signal.SIGINT), which works fine for overriding the SIGINT handler and supporting gdb. That said, the decision to let the terminal send the signal makes it equivalent to how it's currently implemented on Windows, and consistency is a plus.

[pablogsal]

This could have been addressed by changing default_keymap in "Lib/_pyepl/reader.py" to map (r"\x03", "interrupt") instead of mapping it to the ctrl_c command. The interrupt command calls os.kill(os.getpid(), signal.SIGINT), which works fine for overriding the SIGINT handler and supporting gdb. That said, the decision to let the terminal send the signal makes it equivalent to how it's currently implemented on Windows, and consistency is a plus.

The problem of that approach is that if you paste a huge buffer and then want to cancel because pasting it's too slow then you need to wait until you get the key press for Ctrl-C to send the signal, which will happen after all the buffer is processed, while using signals directly allows us to cancel almost immediately

[ambv]

This broke CTRL-C in the asyncio REPL. Now the interrupt and ctrl_c commands are never executed. I need some more time to investigate what happens on Windows to not break that when fixing Linux/Mac.

[ambv]

Fixed by #123799.