[Bug libstdc++/64797] 22_locale/conversions/string/2.cc FAILs

[howarth at bromo dot med.uc.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64797

--- Comment #7 from howarth at bromo dot med.uc.edu ---
(In reply to Jonathan Wakely from comment #6)
> I think this is probably a bug in the test. I was expecting "Stop\\xff\\xff"
> to cause a conversion error, but it is successfully converted to a wide
> string.

Should we just XFAIL selected targets?