mclow.lists added a comment. >> One way we could deal with this is by adding an attribute to the compiler to >> indicate "the const is a lie", that we can apply to std::pair::first, with >> the semantics being that a top-level const is ignored when determining the >> "real" type of the member (and so mutating the member after a const_cast has >> defined behavior). This would apply to all std::pairs, not just the >> node_handle case, but in practice we don't optimize on the basis of a member >> being declared const *anyway*, so this isn't such a big deal right now. > > I'm a fan of this idea, this would also have the bonus of fixing some > pre-existing type-punning between pair<const K, V> and pair<K, V> (see > __hash_value_type and __value_type in <unordered_map> and <map>).
This was //supposed// to be taken care of by [class.mem]/21 (common initial sequence), but that foundered on "standard-layout". https://reviews.llvm.org/D46845 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
