The gift that keeps on giving

[forax at univ-mlv.fr]

oops, i've forgotten to mention that the constructor / factory method known by the serialization should work like a copy constructor.

with your example:
value class X implements Serializable {
   int x;

   public X() { x = 0; }

   public X withX(int x) {
       ALOAD this
       ILOAD x
       WITHFIELD “x”
       ARETURN
   }

   // this constructor is required by the deserialization mechanism otherwise it doesn't compile
  private X(X unsafeXThatComesFromSerialization) {
    this.x = unsafeXThatComesFromSerialization.x;  // checks the arguments here
  }
}

Rémi

----- Mail original -----
> De: "Brian Goetz" <brian.goetz at oracle.com>
> À: "Remi Forax" <forax at univ-mlv.fr>
> Cc: "valhalla-spec-experts" <valhalla-spec-experts at openjdk.java.net>
> Envoyé: Lundi 11 Mars 2019 23:53:14
> Objet: Re: The gift that keeps on giving

> Well, consider this value:
> 
> value class X {
>    int x;
> 
>    public X() { x = 0; }
> 
>    public X withX(int x) {
>        ALOAD this
>        ILOAD x
>        WITHFIELD “x”
>        ARETURN
>    }
> }
> 
> How do I serialize new X().withX(3) ?  How do I deserialize it with the lame
> ctor that X has?
> 
> If you pull on that string, what you end up with is a secret constructor /
> factory that takes one arg per field and initializes all the fields with no
> invariant checking, and serialization scraping the fields and deserialization
> calling that constructor.  Which is about as awful as existing serialization
> (with all the security risks it entails).  So, let’s call that our last choice,
> and look for something better :)
> 
> 
> 
> 
>> On Mar 11, 2019, at 5:26 PM, Remi Forax <forax at univ-mlv.fr> wrote:
>> 
>> Hi Brian,
>> given that a value type is constructed by a factory method (the constructor is
>> desugared to a static method), why not making the serialization aware of that
>> factory method.
>> 
>> Rémi
>> 
>> ----- Mail original -----
>>> De: "Brian Goetz" <brian.goetz at oracle.com>
>>> À: "valhalla-spec-experts" <valhalla-spec-experts at openjdk.java.net>
>>> Envoyé: Lundi 11 Mars 2019 20:30:09
>>> Objet: The gift that keeps on giving
>> 
>>> One thing we need to figure out about value types is … serialization.
>>> 
>>> (Pause for everyone to wishfully say “can’t we just disallow it for values?”,
>>> and three pauses for people to get over this.)
>>> 
>>> The problem is that serialization today proceeds by mutation, which might be
>>> something we could deal with, but the mechanisms for “safer” serialization
>>> (readObject, etc) also rely on mutation, and that’s harder.
>>> 
>>> I’m working on a story here, but for now, let’s just put this on the list of
> >> legacy pain that we will eventually have to deal with.