def main_arena
      return @main_arena.reload! if defined? @main_arena

      off = main_arena_offset
      return if off.nil?

      @main_arena = Arena.new(off + base, size_t, dumper)
    end
def main_arena
      return @main_arena.reload! if defined? @main_arena

      off = main_arena_offset
      return if off.nil?

      @main_arena = Arena.new(off + base, size_t, dumper)
    end
Get the +main_arena+ of libc.
 @return [HeapInfo::Arena]