https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116062
Xi Ruoyao <xry111 at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- See Also| |https://gcc.gnu.org/bugzill | |a/show_bug.cgi?id=111643 Status|UNCONFIRMED |RESOLVED CC| |xry111 at gcc dot gnu.org Resolution|--- |WONTFIX --- Comment #3 from Xi Ruoyao <xry111 at gcc dot gnu.org> --- By adding flatten for a function iterating std::set you are telling the compiler to do an irrational job, so you get irrational result here. It's expected.