warning: src/lib9/fmt/dorfmt.c:64 unreachable code RETURN
warning: src/lib9/fmt/fltfmt.c:184 set and not used: p
warning: src/lib9/utf/utflen.c:35 unreachable code RETURN
warning: src/lib9/utf/utfrrune.c:45 unreachable code RETURN
warning: src/lib9/utf/utfrune.c:44 unreachable code RETURN

LGTM=rsc
R=rsc, iant, gobot
CC=golang-codereviews
https://golang.org/cl/57170052