https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78713
Richard Biener <rguenth at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Keywords| |missed-optimization Status|UNCONFIRMED |NEW Last reconfirmed| |2016-12-09 Component|tree-optimization |libstdc++ Ever confirmed|0 |1 --- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> --- Depends on the size of the optional thing of course. A libstdc++ issue, the middle-end can not know it is allowed to clobber the destination here.