This is not the only case. It harms not only performance, but also conformance, e.g. https://developercommunity.visualstudio.com/t/unable-to-move-stdpackaged-ta

This is not the only case. It harms not only performance, but also conformance, e.g. https://developercommunity.visualstudio.com/t/unable-to-move-stdpackaged-task-into-any-stl-conta/108672 https://developercommunity.visualstudio.com/t/unable-to-move.... Microsoft is stupid enough since the first decision of the implementation impacting the ABI is made. There was no one enforcing such bad decisions shipped into the productions at the very beginning. Both libstdc++ and libc++ have more flexible rules to preventing ABI breakage.