I think that should be taken up with the xstring maintainers.
I don't think there is any reasonable way to say you can comment out parts
of a file in a different encoding.
The file encoding specifies the byte stream interpretation before any tex
tokenization
If the file can not be interpreted as utf-8 then it can't be interpreted at
all. Even replacing by U+FFFD
is being lenient.
David
On Sun, 21 Feb 2021 at 11:04, jfbu <j...@free.fr> wrote:
> Hi,
>
> consider this
>
> \documentclass{article}
> \usepackage{xstring}
> \begin{document}
> \end{document}
>
> and call it xexstring.tex
>
> Then xelatex xexstring triggers 136 warnings of the type
>
> Invalid UTF-8 byte or sequence at line 35 replaced by U+FFFD.
>
> Looking at file
>
> /usr/local/texlive/2020/texmf-dist/tex/generic/xstring/xstring.tex
>
> I see that this matches with use of latin-1 encoded characters in comments.
>
> Notice that it is a not a user decision here to use a latin-1
> encoded file.
>
> In fact I encountered this in a file I was given where
> xstring package was loaded by another package.
>
> Regards,
>
> Jean-François
>
>
>
