A new WG21 paper is available. A copy is linked below, and will also appear in the next normal WG21 mailing. If you are not a committee member, please use the comments section below or the std-proposals forum for public discussion.
Document number: N4041
by Jonathan Wakely
In Issaquah there were proposals targeting a TS which enhanced existing types in the Standard Library, in particular N3857 which modifies
std::future, N3916 which modifies
std::packaged_task, and N3920 which modifies
Following straw polls the decision was taken to allow a TS to change existing types in namespace std, so that users who opt in to use the TS (via some implementation defined means) get the enhanced versions without needing to change any code. ...The decision made following the straw polls means for an implementation to ship a TS they must change existing classes in their implementation, which has the potential to make silent ABI changes to users' programs. ...
These issues can make it complicated for implementers to provide TS support, so that users have to wait longer before they have access to an implementation, which then makes it less likely the committee will get useful and timely feedback on the TS contents.