Erlang 26 breaks command line on Windows

[Intelliractive]

Describe the bug

• After further actions dialog appears (that one that appears after ^c), some buttons start (like arrows and Alt) producing incoherent mess (similar to special symbol combinations usually used for making coloured text in Windows CMD and Powershell).

• In June(June 26, particularly), when I experienced the issue the first time, even Clipdiary, a clipboard manager, used to break.

• The backspace key starts deleting whole words.

backspace.by.word.mp4

broken.clipdiary.mp4

normal.clipdiary.example.mp4

The Dialog is used and the console is now broken

The Dialog is skipped with another Ctrl-C, fine

The problem is definitely caused by that menu

To Reproduce
Run any BEAM app and pick a further action

Expected behavior
The console doesn't break

Affected versions
26

Notes
I suspect the disappearance of the GUI app and this flaw are linked.

[frazze-jobb]

Related #7548

[user20230119]

Was this fixed in 26.1.2?

[garazdawi]

The fix is to be released in 26.2.

Sine GitHub does not notify when issues are updated I never noticed that this issue had been updated with more bug reports, so not all bugs listed above have been fixed yet. I’m therefore re-opening this issue.

[thojanssens]

Thank you for working on this. This has been a pain.

May I ask, does this happen because... Windows sucks? Would this kind of problem ever happen on Linux? Or MacOS?

[garazdawi]

The same issue has been present on most other platforms. Here is an example here we fixed the same issue on MacOS: #3796. So in this partucular case, Windows is not worse than most others 😄

One of the things were Windows is not as good as the other platforms is the fact that it is very difficult/impossible to write automated tests for the console. So it is very easy for us to change something and not knowing that it breaks on Windows until someone reports it. We do some manual testing, but it is hard to test everything that our automated tests on other platforms test.

[user20230119]

@thojanssens I switched to PowerShell as it doesn't have this issue.

[Intelliractive]

@thojanssens I switched to PowerShell as it doesn't have this issue.

I have also done that, but the issue is still there on cmd

[joeapearson]

I'm finding that OTP 26.2.1 (latest at the time of writing) + Elixir 1.16.0 will hang on Windows 11. The behaviour is intermittent but reproduces more often than not. I assume that the issue I'm encountering is related to those described on this issue hence posting here.

The application continues running but nothing is echo'd back to me on the console when I attempt to interact with it. Pressing Ctrl+C a couple of times exits as expected, (perhaps) interestingly printing the BREAK message several times (more times than I would otherwise expect).

It does seem like I can cause the command prompt to stay alive and continue accepting input as expected by (and I know this sounds silly) pressing return a bunch of times as soon after startup as I can.

I've reproduced in these combinations:

• PowerShells v1 and v7 via Windows terminal
• cmd.exe via Windows terminal
• PowerShells v1 and v7 via the Windows console host
• cmd.exe via the Windows console host

I can revert to OTP 25 of course but the promise of being able to work without werl.exe is a good one.

It seems to be very difficult to get any useful information out of iex when it is stuck. Can anyone suggest a good way of extracting useful information that I could add to this issue and/or a means of resolving it?

[garazdawi]

If you do "Ctrl+Break" then "A" and then "Enter" you will create a crash dump of you system called erl_crash.dump. You can then use crashdump viewer to view the dump and dig around so see what is going on. If nothing if private in the dump, feel free to post it here and I can have a look.

[joeapearson]

@garazdawi thanks for the offer.

Here's an erl_crash.dump as requested.

erl_crash.zip

[joeapearson]

@garazdawi In the most polite recognising-that-you-must-have-plenty-of-other-stuff-to-do way, is there any chance that you might have found anything useful in that crash log that I attached on the previous reply to this message? Thanks for any help you're able to provide.

[garazdawi]

Thanks for the ping, I had forgotten that you added a dump. From what I can tell Elixir has not started the reading end of the tty (that is shell:start_interactive/0 has not been called). Maybe @josevalim can shed some light on when that may happen?

[josevalim]

@joeapearson which command (elixir, mix, iex, etc) do you run when you see the hanging?

[garazdawi]

Seems to be iex -S mix.

If you open the dump using crash dump viewer you will see the command line options in the stacktrace of the init process.

[josevalim]

Thank you @garazdawi! Looking at the user_drv process in the crash dump, I can see IEx.Shell as part of a group, which makes me think we did call shell:start_interactive/1, no?

@joeapearson if you are running iex -S mix, it will first attempt to compile the current project. Has compilation already finished by the time you notice it is stuck?

In order to support both Erlang/OTP 26 and earlier, our boot process goes like this.

1. First create a file called custom_user.erl with the following:

-module(custom_user).
-compile(export_all).
start() -> user_drv:start(#{initial_shell => noshell}).

2. Compile it: erlc custom_user.erl

3. Now run: erl -noshell -user custom_user -eval "spawn(fun() -> shell:start_interactive() end)"

@joeapearson can you try reproducing the issue with the steps above? You can try executing the third step several times.

[garazdawi]

Thank you @garazdawi! Looking at the user_drv process in the crash dump, I can see IEx.Shell as part of a group, which makes me think we did call shell:start_interactive/1, no?

Yes, you are right. I thought I checked there but apparently not. Seems like this is an issue in our code. Sorry for the noise.

For some reason the reader process has crashed... I wonder why...

[josevalim]

No worries, I am also glad to help trim down any issue that involves Elixir so you have to debug only Erlang (and not Elixir).

[garazdawi]

@joeapearson when github actions has finished with #8103 it will produce a windows installer with an Erlang with some extra logs for when the tty reader crashes. If you could have a go and see if you can reproduce the behaviour with that version of Erlang that would be great. If you can reproduce it, then please attach the crash dump again so that I can view it.

[garazdawi]

ping @joeapearson, do you have some time to reproduce the error or should I close this issue?

[simonmcconnell]

I thought I'd give OTP 26 another go but I'm getting an intermitent error running the latest (OTP 26.2.5, Elixir 1.16.2-otp-26) when using Windows Powershell, Command Prompt or Powershell Core (aka Powershell).

R:\>erl -noshell -user -custom_user -eval "spawn(fun() -> shell:start_interactive() end)"
Erlang/OTP 26 [erts-14.2.5] [source] [64-bit] [smp:48:32] [ds:48:32:10] [async-threads:1] [jit:ns]

Eshell V14.2.5 (press Ctrl+G to abort, type help(). for help)
=CRASH REPORT==== 3-May-2024::13:36:47.186000 ===
  crasher:
    initial call: prim_tty:reader/1
    pid: <0.68.0>
    registered_name: user_drv_reader
    exception error: no case clause matching {error,
                                              {'GetOverlappedResult',
                                               'The I/O operation has been aborted because of either a thread exit or an application request.\r\n'}}
      in function  prim_tty:reader_loop/6 (prim_tty.erl, line 476)
    ancestors: [user_drv,<0.64.0>,kernel_sup,<0.47.0>]
    message_queue_len: 0
    messages: []
    links: [<0.65.0>]
    dictionary: []
    trap_exit: false
    status: running
    heap_size: 376
    stack_size: 28
    reductions: 156
  neighbours:

in iex.bat -S mix

2024-05-03 13:32:45.297 [error] Process :user_drv_reader (#PID<0.68.0>) terminating
** (CaseClauseError) no case clause matching: {:error, {:GetOverlappedResult, :"The I/O operation has been aborted because of either a thread exit or an application request.\r\n"}}
    (kernel 9.2.4) prim_tty.erl:476: :prim_tty.reader_loop/6
    (stdlib 5.2.3) proc_lib.erl:241: :proc_lib.init_p_do_apply/3
Initial Call: :prim_tty.reader/1
Ancestors: [:user_drv, #PID<0.64.0>, :kernel_sup, #PID<0.47.0>]
Message Queue Length: 0
Messages: []
Links: [#PID<0.66.0>]
Dictionary: []
Trapping Exits: false
Status: :running
Heap Size: 376
Stack Size: 28
Reductions: 180 ~

[garazdawi]

strange, what you are doing "works on my machine". How often do you get that error?

[simonmcconnell]

I think it was almost every time with Windows Powershell and Command Prompt and less often with Powershell Core. Originally I thought Powershell Core worked because it ran fine a few times.