Thank you for the report.
I copied your file texi-index-bug.texi and ran pdfetex on it. I got a correct
UTF-8 encoded output, which I've attached.
On Fri, Jul 28, 2017 at 08:13:03PM +0200, Vincent Belaïche wrote:
> Hello,
>
> Attached is a minimal example.
>
> I don't know who is to blame, is that Texinfo, or MikTeX, as I updated
> the latter lately.
>
> Look at the .cp file, I get a spurious space in between the bytes of any
> UTF-8 charcters that do not fit in a single byte (there are plenty of
> those in French, like é or ù).
>
> I suspect that Texinfo lets the active characters active when \write-ing
> the non sorted index file, and the MikTeX inserts a whitespace like
> after any command.
I doubt it, but don't know for certain.
I know there can be differences between TeX engines in how byte values
128-255 are handled.
I will look at the patches you sent and see if they make a difference to
anything.
\entry{Où t'es tu cachée, bien aimée ?}{1}{Où t'es tu cachée, bien aimée
?}
