<div dir="ltr"><div>This report is from "user202729" on StackExchange, just reporting here on their behalf in case they don't get around to it: <a href="https://tex.stackexchange.com/a/649069">https://tex.stackexchange.com/a/649069</a></div><div><br></div><div>Boiled down to a plain TeX case by Phelype Oleinik:<br></div><div><br></div><div>\def\weird{\expandafter\weirda\expandafter{\iffalse}\fi}<br>\def\weirda#1{\expandafter\weirdb\noexpand}<br>\def\weirdb#1{\iffalse{\fi}#1\edef\mycontainendwrite{\noexpand#1}}<br>\immediate\write16{\weird}<br>\expandafter\let\expandafter\myendwrite\mycontainendwrite<br>\bye<br></div><div><br></div><div>(The last \bye is optional as the crash happens before it.)</div><div><br></div><div><br></div></div>