notcurses-info hangs from VSCode and Windows terminals when running over SSH

[xaviershay]

I have built notcurses on a remote debian machine. notcurses-info (and indeed, all notcurses- binaries) appear to hang when launched. It seems very likely that TERM and the like aren't set up properly ... but given it doesn't work on multiple different emulators even after setting recommend settings, it feels like at least a bug in documentation. I also feel that hanging is bad and it should probably exit?

Environments

MS Terminal (Windows)

• export | egrep 'LANG|LC_CTYPE|TERM'

I tried both the default:

$ export | egrep 'LANG|LC_CTYPE|TERM'
declare -x LANG="en_AU.UTF-8"
declare -x LANGUAGE="en_AU:en"
declare -x TERM="xterm-256color"

and also those recommended in TERMINALS.md

$ export | egrep 'LANG|LC_CTYPE|TERM'
declare -x COLORTERM="24bit"
declare -x LANG="en_AU.UTF-8"
declare -x LANGUAGE="en_AU:en"
declare -x TERM="ms-terminal"

both exhibited the same behaviour

• notcurses version (available from notcurses-demo i)
  notcurses-demo hangs, but I compiled from source:

Verbose output is here

$ git branch
* (HEAD detached at v3.0.16)
$ uname -a
Linux apollo 6.1.0-38-amd64 #1 SMP PREEMPT_DYNAMIC Debian 6.1.147-1 (2025-08-02) x86_64 GNU/Linux

• terminal name + version

Microsoft Terminal 1.22.12111.0

VSCode Terminal (Windows)

$ export | egrep 'LANG|LC_CTYPE|TERM'
declare -x COLORTERM="truecolor"
declare -x LANG="en_AU.UTF-8"
declare -x LANGUAGE="en_AU:en"
declare -x TERM="xterm-256color"
declare -x TERM_PROGRAM="vscode"
declare -x TERM_PROGRAM_VERSION="1.104.1"

Version: 1.104.1 (system setup)
Commit: 0f0d87fa9e96c856c5212fc86db137ac0d783365
Date: 2025-09-17T23:36:24.973Z
Electron: 37.3.1
ElectronBuildId: 12404162
Chromium: 138.0.7204.235
Node.js: 22.18.0
V8: 13.8.258.31-electron.0
OS: Windows_NT x64 10.0.26100

Alacritty (Windows)

Did not work by default, but got at least some results after setting recommended settings

VSCode (Mac)

As above VSCode, same behaviour.

iTerm2 (Mac)

It works!!!!

(Though terminal is left corrupted after exiting notcurses-demo by pressing q)

Potentially related issues

• after installing notcurses on windows 10 wsl2 ubuntu 18 lts... blank output #2689 is pretty light on, but matches the behaviour I observe.
• notcurses-tester hangs on windows #2363 is a hang, but more likely related to windows build behaviour?
• notcurses-info hangs after failure building automaton #2644 another hang, also perhaps more likely related to windows build behaviour?

[mdiiorio]

I support a tool that uses Notcurses and I've heard from users that they're seeing hangs after upgrading to the new Mac OS, Tahoe. I wonder if it's a similar issue? I'm going to try to repro once I get access to a machine with Tahoe.

[RickieBlaese]

Same hanging here with notcurses-demo and notcurses-tester in WSL2 running inside of Windows Terminal & Terminal Preview (notcurses was built from most recent source as RelWithDebInfo). Notably, it hangs close to 90% of the time and sometimes works properly.
Using gdb, both notcurses-demo and notcurses-tester hang inside of handle_responses in interrogate_terminfo.
Specifically, notcurses-demo does not print anything before hanging, and notcurses-tester hangs after printing

Running with LANG=en_US.UTF-8
Running with TERM=xterm-256color

Outside of gdb, notcurses-tester hangs most of the time at the above point but sometimes progresses to

Running with LANG=en_US.UTF-8
Running with TERM=xterm-256color
Detected cell geometry: 184x60
[doctest] doctest version is "2.4.11"
[doctest] run with "--help" for options

after which a CTRL-C leads to

===============================================================================
/home/user/notcurses/src/tests/autogrow.cpp:3:
TEST CASE:  Autogrow

/home/user/notcurses/src/tests/autogrow.cpp:3: FATAL ERROR: test case CRASHED: SIGINT - Terminal interrupt signal

===============================================================================
[doctest] test cases: 1 | 0 passed | 1 failed | 45 skipped
[doctest] assertions: 0 | 0 passed | 0 failed |
[doctest] Status: FAILURE!

Extra info:

In Windows Terminal, running notcurses-demo with strace -f -o /dev/null -D ./notcurses-demo almost never hangs the first time in a new terminal instance.
However, quitting (either gracefully with 'q' or CTRL-C) and running it again in the same terminal instance with the same command hangs roughly 50% of the time.
The situation is similar for notcurses-tester with strace -f -o /dev/null -D ./notcurses-tester, except that the working case for notcurses-demo corresponds to the longer output case of notcurses-tester (same output as seen above with "TEST CASE: Autogrow").

In XTerm, both notcurses-demo and notcurses-tester function normally without any strace shenanigans, and notcurses-tester passes all of 45 tests.

In conhost, the older Windows console host, strace does not appear to affect the rate of success of notcurses-demo, and neither does the first run in a new instance.
The behavior is also the same for notcurses-tester, except for that notcurses-tester sometimes gets further when running with strace and stops instead at the Blit or Cell test case, with > 0 assertions passed. In general, conhost seems to succeed more often than either of the strace or non-strace commands in Windows Terminal.

All of the above were in the same WSL2 instance, with COLORTERM not set. Setting COLORTERM=truecolor appears to, at least in most cases, increase the likelihood of success, although it can cause strange behavior in conhost.

Hopefully some of this weird info is helpful.