#! /usr/bin/env stap

global var%, varerr

probe $1 {
  if (@defined($2)) {
     try {
         newvar = $2;
         if (var[tid()] != newvar) {
            printf("%s[%d] %s %s:\n", execname(), tid(), pp(), @2);
            println(newvar);
            var[tid()] = newvar;
         }
     } catch { varerr ++ }  # error during $2 resolution or perhaps var[] assignment
  }
}

probe error,end {
  if (varerr) printf("%s %s access errors: %d", @1, @2, varerr);
}