[Bug c++/108669] missing error when std::vector of incomplete type has member referenced

[ldalessandro at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108669

--- Comment #3 from Luke Dalessandro <ldalessandro at gmail dot com> ---
(In reply to Jonathan Wakely from comment #2)
> (In reply to Luke Dalessandro from comment #0)
> > This should run afoul of the second half of
> > https://eel.is/c++draft/vector#overview-4. "T shall be complete before any
> > member of the resulting specialization of vector is referenced."
> > 
> > I honestly don't know if that "shall" implies this is ill-formed or
> > undefined behavior.
> 
> The standard only defines the behaviour if T is complete, and so otherwise
> it's undefined.
> 
> In library wording we try to say explicitly when something makes the program
> ill-formed.

Thanks Johnathan. From that perspective this is simply a QoI diagnostic request
to normalize behavior. If you want to drop the accepts-invalid tag I don’t
mind.