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.