ref: ac4840116ef15e2fc65d0e68f7e16d3a8a1aa2f8 dir: /sys/src/cmd/unix/drawterm/libc/runestrlen.c/
#include <u.h> #include <libc.h> long runestrlen(Rune *s) { return runestrchr(s, 0) - s; }