[asyncify]: asyncify_stop_unwind throws a RuntimeError: unreachable

Hi,

I am hitting an abort() when maybeStopUnwind is called after I refactored a pthread_create wrapper that sets and cancels the mainloop (to allow correctly joining the thread as a workaround to #17552).

Replacing the abort in runAndAbortIfError with a console.error to get the exception I get this trace :

RuntimeError: unreachable
    at asyncify_stop_unwind (experimental.wasm:0x35470b3)
    at ret.<computed> (experimental.js:7561:35)
    at experimental.js:1152:22
    at runAndAbortIfError (experimental.js:7449:16)
    at Object.maybeStopUnwind (experimental.js:7584:11)
    at ret.<computed> (experimental.js:7566:30)
    at Object.doRewind (experimental.js:7628:16)
    at experimental.js:7661:47

runAndAbortIfError	@	experimental.js:7451
maybeStopUnwind	@	experimental.js:7584
ret.<computed>	@	experimental.js:7566
doRewind	@	experimental.js:7628
(anonymous)	@	experimental.js:7661
Promise.then (async)		
(anonymous)	@	experimental.js:7721
handleSleep	@	experimental.js:7639
handleAsync	@	experimental.js:7719
__asyncjs__init_js_file	@	experimental.js:1360
imports.<computed>	@	experimental.js:7527
$EmFileOpen	@	experimental.wasm:0x45dd42
$generic_start	@	experimental.wasm:0x31c049c
$vlc_module_load	@	experimental.wasm:0x31bfcfa
$module_need	@	experimental.wasm:0x31c0194
$access_New	@	experimental.wasm:0x3279fa4
...

Sorry for not being able to provide a short sample, I tried fiddling with the one in #17552 but could not reproduce.

asyncify_stop_unwind is called regularly, and when it is called after this function or this function, I am having this abort().

Version of emscripten/emsdk:

$ emcc -v 
emcc (Emscripten gcc/clang-like replacement + linker emulating GNU ld) 3.1.17 (fbc532773d84d2bd7da876275671970e792ad1cd)
clang version 15.0.0 (https://github.com/llvm/llvm-project 17e4c217b66305e60657a48f10fe3c428c2fe4d2)
Target: wasm32-unknown-emscripten

Bắt đầu với src/library_async.js, quanh runAndAbortIfError, maybeStopUnwind và doRewind, sau đó kiểm tra lệnh gọi asyncify_stop_unwind trong trace được tạo. Tái hiện và thu gọn kịch bản VLC pthread/mainloop được liên kết, bao gồm các hàm được tham chiếu, để cô lập lỗi; công việc được xem là hoàn tất khi đã xác nhận nguyên nhân kèm theo coverage hồi quy hoặc một hướng sửa lỗi chính xác được maintainer phê duyệt.