anchor.diff:      [Failed | Rec] = Acc,
       [[{rc(Avp), Avp} | Failed] | Rec];
   
  -%% No AVP of this name: try to pack as 'AVP'.
  -acc2(Acc, Avp, I, Name, AvpName, 0, Strict, Mod, Opts) ->
  -    M = Avp#diameter_avp.is_mandatory,
  -    Arity = pack_arity(Name, AvpName, Opts, Mod, M),
  -    acc2(Acc, Avp, I, Name, 'AVP', Arity, Strict, Mod, Opts);
  -
   %% Relaxed arities.
   acc2(Acc, Avp, _, _, AvpName, Arity, Strict, Mod, _)
     when Strict /= decode ->
  
positive.code: 
  incr(Name, Code, Vid, M, Mod, Strict, Opts, AM0) ->
      NameT = Mod:avp_name(Code, Vid), %% {AvpName, Type} | 'AVP'
      AvpName = field(NameT),
      Arity = avp_arity(Name, AvpName, Mod, Opts, M),
      {NameT, AvpName, Arity, incr(AvpName, Arity, Strict, AM0)}.
  
  %% Data is a truncated header if command_code = undefined, otherwise
  %% payload bytes. The former is padded to the length of a header if
  
negative.code: 
  %% incr/4
  
  incr(_, A, SA, AM)
    when A == ?ANY;
         A == 0;
         SA /= decode ->
      {undefined, AM};
  