[Bug libstdc++/84110] Null character in regex throws std::regex_error

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84110

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
I agree ECMAScript should treat NUL as an ordinary char. POSIX doesn't though:

"The interfaces specified in POSIX.1-2017 do not permit the inclusion of a NUL
character in an RE or in the string to be matched. If during the operation of a
standard utility a NUL is included in the text designated to be matched, that
NUL may designate the end of the text string for the purposes of matching."

I'm not sure how that is supposed to translate to std::regex.