Proposed resolution:

Change the specification in table 68 "Optional Sequence Operations" in 23.1.1/12 for "a.back()" from

*--a.end()

to

  { iterator tmp = a.end(); --tmp; return *tmp; }

and the specification for "a.pop_back()" from

a.erase(--a.end())

to

  { iterator tmp = a.end(); --tmp; a.erase(tmp); }