bug#31274: 27.0.50; xdisp.c:7575: Emacs fatal error: assertion failed: IT_BYTEPOS (*it) == CHAR_TO_BYTE (IT_CHARPOS (*it))

[Eli Zaretskii]

> From: Stefan Monnier <monnier@IRO.UMontreal.CA>
> Date: Thu, 26 Apr 2018 15:54:55 -0400
> 
> Package: Emacs
> Version: 27.0.50
> 
> I can reproduce the above assertion failure when I do the following:
> 
>     % src/emacs -Q /usr/bin/perl -l 
> .../elpa/packages/nhexl-mode/nhexl-mode.el -f nhexl-mode --eval '(setq 
> word-wrap t)'
>     y
>     M->

I cannot reproduce this, with today's master of Emacs and of ELPA.  I
tried on GNU/Linux (in -nw) and on MS-Windows (in a GUI session), and
both didn't trigger the assertion (tried with 3 executables, including
those you mentioned).  I'm guessing some particular byte sequence
present in your binaries triggers this.  So please provide more
details.

P.S.  I frequently wonder why veteran experienced users omit crucial
information from their bug reports, such as the C backtrace in this
case, that is very easy for them to collect.  Please don't ever assume
that something which is 100% reproducible on your system can be
similarly easily reproduced on any other system, and that therefore
those details are an unnecessary luxury.