[PATCH][_GLIBCXX_DEBUG] Improve valid_range check

[Stephan Bergmann]

On 26/11/2019 20:07, François Dumont wrote:
> However I wasn't sure about this syntax before the commit so I had run 
> the new 2_neg.cc with:
> 
> make CXXFLAGS=-std=c++98 check-debug
> 
> and it worked fine and still is !
> 
> I also try -std=gnu++98 and made sure that pch had been updated by 
> re-building libstdc++ first. I just can't get the expected compilation 
> error.
> 
> Maybe I need to rebuild the whole stuff to get an error...

I saw the error with recent Clang and -std=gnu++98.  Recent GCC indeed 
seems to give at most a warning.