[Bug libstdc++/59170] pretty printers: end iterator invalid pointer

["redi at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59170

--- Comment #13 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Jan Kratochvil from comment #11)
> (In reply to Jonathan Wakely from comment #9)
> > Most developers don't even know the debug mode exists.
> 
> That's a problem communicating it to users.  -O0 -g would be best to always
> use -D_GLIBCXX_DEBUG if there is a way how to solve the ABI compatibility
> problem.

That's a HUGE if.

There is no plan to make debug mode ABI compatibile, so it's impossible to use
in many cases (e.g. linking to pre-built third-party libs that use C++ types in
the API).

Anyway, I am testing some patches to improve printing of invalid iterators
(both debug mode and normal).