[polyml] addPrettyPrinter type security

Thanks, Rob. I've applied your patch. David

On 09/01/2016 15:27, Rob Arthan wrote:

PolyML.addPrettyPrinter checks its printArgTypes parameter carefully when you are installing a pretty-printer for a polymorphic type. As far as I can see it guarantees type security for polymorphic types.

However, when you install a pretty-printer for a monomorphic type, the parameter isn't checked at all. E.g., the following code doesn't result in any error messages and ends by crashing poly.

datatype MONO = Mono of int;

fun pp_mono1 _ (i : int) (Mono j) = ( PolyML.PrettyString (Int.toString (i + j)) );

PolyML.addPrettyPrinter pp_mono1;

Mono 42; (* Prints "val it = 42: MONO" - apparently i was 0 *)

fun pp_mono2 _ (r : int ref) (Mono _) = ( PolyML.PrettyString (Int.toString (!r)) );

PolyML.addPrettyPrinter pp_mono2;

Mono 42; (* Crashes *)

Shouldn't processArgTypes be required to have type unit when defining a pretty-printer for a monotype? The patch below implements this check and tries to improve the error message (which is already a bit misleading if you get something wrong for a type with more than one parameter).

Regards,

Rob.

diff --git a/mlsource/MLCompiler/VALUE_OPS.ML b/mlsource/MLCompiler/VALUE_OPS.ML index 1535d4f..9e00f0d 100644 --- a/mlsource/MLCompiler/VALUE_OPS.ML +++ b/mlsource/MLCompiler/VALUE_OPS.ML @@ -958,8 +958,8 @@ struct val typeVars = List.tabulate(arity, fn _ => mkTypeVar (0, false, true, false)) val tupleType = case typeVars of

•                            [] => (* No arg so we can have anything here. *)
  

•                                mkTypeVar (generalisable, false, false, false)
  

•                            [] => (* No arg so must have unit. *)
  

• 		    unitType
                       |   [arg] => mkFn arg (* Just a single function. *)
                       |   args => mkProductType(List.map mkFn args)
                   val addPPType = mkFunctionType(argPrints, mkFunctionType(installType, pretty))
  

@@ -970,7 +970,7 @@ struct in checkPPType(addPPType, testType, "addPrettyPrint", lex, loc, fn () =>

•                            PrettyString "addPrettyPrint element functions must have type 'a * int -> pretty")
  

•                            PrettyString "addPrettyPrint element functions must have type 'a * int -> pretty, 'b * int -> pretty, ... with one function for each type parameter")
                  end;
  
          (* Only report the error when the function is run.  Because addPrettyPrint is
  
  
  

---

polyml mailing list polyml at inf.ed.ac.uk http://lists.inf.ed.ac.uk/mailman/listinfo/polyml