On Fri, Mar 2, 2018 at 11:07 AM, Nathan Sidwell <nat...@acm.org> wrote: > Jason, Jakub, > I've simplified the testcase Padraig provided and attached it to > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84497 > > Notice that 'Base::Base ()' is not a constexpr ctor, because the integer > member is not initialized. That means 10.1.4/4.5 is unsatisfied. So struct > Base gets its 'has_constexpr' flag set via the Base::Base (int) ctor. > struct Derived is not so lucky, and 'has_constexpr' is unset. > > Thus we end up with an unsatisfied strong reference to _ZTH11derived_obj > > NEEDS_CONSTRUCTING && !HAS_CONSTEXPR_CTOR is insufficient to determine > whether there must be an init fn. > > While the patch does indeed work, it may be too pessimal, making the > reference weak in more cases than necessary. > > NEEDS_CONSTRUCTING && !HAS_CONSTEXPR_CTOR && !HAS_DEFAULT_CONSTRUCTOR seems > like it would be sufficient. and indeed that works in this case.
Do you mean !HAS_TRIVIAL_DFLT rather than !HAS_DEFAULT_CONSTRUCTOR? That makes sense to me. Jason
