https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84843
Jakub Jelinek <jakub at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |jason at gcc dot gnu.org --- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> --- The ICE is because of assertion that DECL_INITIAL is non-NULL; when duplicate_decls is called, olddecl is the builtin from builtins.def with NULL DECL_INITIAL, and newdecl is the user definition with error_mark_node as DECL_INITIAL. If the pedwarn errors, I guess we could return error_mark_node instead of olddecl and the error-recovery would work fine, but for -fpermissive I have no idea what to do, except for returning NULL_TREE, but that is something you didn't like.