>
> OK for trunk, thanks!
>
> I think this is OK to backport to 13 too.
>
> Maybe after this we can define the __cpp_lib_null_itetators macro for 
> debug mode?
>
After this fix of local_iterator I think we can indeed.

In fact the added 11316.cc was already passing for 
unordered_set<>::local_iterator but simply because we were missing the 
singular check. Both issues solved with this patch.

I found the version.def file to cleanup but no idea how to regenerate 
version.h from it so I'll let you do it, ok ?

     libstdc++: Fix _Safe_local_iterator<>::_M_valid_range

     Unordered container local_iterator range shall not contain any singular
     iterator unless both iterators are value-initialized.

     libstdc++-v3/ChangeLog:

             * include/debug/safe_local_iterator.tcc
             (_Safe_local_iterator::_M_valid_range): Add 
_M_value_initialized and
             _M_singular checks.
             * testsuite/23_containers/unordered_set/debug/114316.cc: 
New test case.


Ok to commit ?

François