Re: Scan of regexps in Emacs (March 17)

[Noam Postavsky]

On Tue, 2 Apr 2019 at 10:15, Mattias Engdegård <address@hidden> wrote:

> > After looking into it I realized that I don't really know the semantics 
> > here (the text I recently added there seems to be wrong, in some cases), 
> > and I have my doubts that anyone else knows the semantics either. The 
> > attached patch simply gets rid of that section, leaving the area 
> > undocumented. User beware!
>
> Apparently I don't really know it either -- I just discovered that:
>
> (string-match "\xff"     "\xff")  => 0
> (string-match "[\xff]"   "\xff")  => 0
> (string-match "\xffé?"   "\xff")  => nil
> (string-match "[\xff]é?" "\xff")  => 0
> (string-match "\xff"     "\xffé") => 0
> (string-match "[\xff]"   "\xffé") => nil
> (string-match "\xffé?"   "\xffé") => 0
> (string-match "[\xff]é?" "\xffé") => nil

See also Bug#3687.

https://debbugs.gnu.org/cgi/bugreport.cgi?bug=3687