C++草案指出:12.8p31Thiselisionofcopy/moveoperations,calledcopyelision,ispermittedinthefollowingcircumstances(whichmaybecombinedtoeliminatemultiplecopies):(...)whenatemporaryclassobjectthathasnotbeenboundtoareference(12.2)wouldbecopied/movedtoaclassobjectwiththesamecv-unqualifiedtype,thecopy/moveoper