https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108846
--- Comment #12 from Giuseppe D'Angelo <dangelog at gmail dot com> --- (In reply to Jonathan Wakely from comment #9) > (In reply to Giuseppe D'Angelo from comment #5) > > https://github.com/gcc-mirror/gcc/blob/master/libstdc%2B%2B-v3/include/bits/ > > stl_algobase.h#L417-L437 > > > > Is the extent of the fix just to add another branch to the if (_Num) check > > here? > > Yes, I think that's the simplest place to fix it. > > And we can even get rid of the static assertion, because the Num==1 branch > will require assignability now. > > --- a/libstdc++-v3/include/bits/stl_algobase.h > +++ b/libstdc++-v3/include/bits/stl_algobase.h > @@ -737,16 +737,11 @@ _GLIBCXX_END_NAMESPACE_CONTAINER > static _Tp* > __copy_move_b(const _Tp* __first, const _Tp* __last, _Tp* __result) > { > -#if __cplusplus >= 201103L > - using __assignable = __conditional_t<_IsMove, > - is_move_assignable<_Tp>, > - is_copy_assignable<_Tp>>; > - // trivial types can have deleted assignment > - static_assert( __assignable::value, "type must be assignable" ); > -#endif > const ptrdiff_t _Num = __last - __first; > - if (_Num) > + if (__builtin_expect(_Num > 1, true)) > __builtin_memmove(__result - _Num, __first, sizeof(_Tp) * _Num); > + else if (_Num == 1) > + *__result = *__first; > return __result - _Num; > } > }; If this code path also takes care of std::move(b,e,o), then this doesn't sound correct -- for _Num==1 and _IsMove==true, then it should use a move assignment (std::move(*__first)). But then that std::move doesn't actually work as __first is a pointer to const...
