counter.vhdl:25:8:warning: incomplete sensitivity list, signal "ena" is missing [-Wsensitivity]
    if ena = '1' then
       ^
counter.vhdl:26:17:warning: incomplete sensitivity list, signal "cont" is missing [-Wsensitivity]
      n_cont <= cont + 1;
                ^
counter.vhdl:23:18:warning: extra signal "rst" in sensitivity list [-Wsensitivity]
  comb: process (rst)
                 ^
