Condy bsm should be idempotent

[forax at univ-mlv.fr]

----- Mail original -----
> De: "Brian Goetz" <brian.goetz at oracle.com>
> À: forax at univ-mlv.fr
> Cc: "amber-spec-experts" <amber-spec-experts at openjdk.java.net>
> Envoyé: Jeudi 17 Août 2017 20:07:28
> Objet: Re: Condy bsm should be idempotent

> So, this is more of a purity requirement -- that the result of the
> bootstrap be consistently derived from its arguments and no other
> state.  But you are not asking for heroic interning -- just that the
> bootstraps not do anything "funny".  (This is in the same category as
> "the result should be a constant", though neither the language nor VM
> can enforce this.)   Right?

yes !

Rémi

> 
> On 8/17/2017 1:50 PM, forax at univ-mlv.fr wrote:
>> ----- Mail original -----
>>> De: "Brian Goetz" <brian.goetz at oracle.com>
>>> À: forax at univ-mlv.fr
>>> Cc: "amber-spec-experts" <amber-spec-experts at openjdk.java.net>
>>> Envoyé: Jeudi 17 Août 2017 19:35:33
>>> Objet: Re: Condy bsm should be idempotent
>>> This is going to be problematic for bootstraps that produce, e.g.,
>>> arrays; their equals() method delegates to Object.equals(), which means
>>> such bootstraps would have to maintain an (expensive!) cache for interning.
>> fully agree,
>> i've forget the case of array,
>> structurally equivalent <=> == for primitives, Object.equals for objects and
>> Arrays.equals() for arrays.
>>
>>> It is an old problem that constant resolution can be racy, but we would
>>> like for the JVM to manage the race, not the bootstraps.
>> either we specify that the BSM has to be idempotent and the VM doesn't have to
>> enforce that,
>> the other solution is to say that the semantics of condy allow the resolved
>> constant to be a result of a previous call of the BSM with the same arguments.
>>
>> also, if we want to be able to resolve condy at jlink time, we also need the
>> same kind of wordings, because currently a BSM can depend on the daytime.
>>
>> Rémi
>>
>>> On 8/17/2017 1:30 PM, forax at univ-mlv.fr wrote:
>>>> equals,
>>>> if they are structurally equivalent, same name, same descriptor, same bsm and
>>>> same bsm arguments,
>>>> they should produce the same result.
>>>>
>>>> Rémi
>>>>
>>>> ----- Mail original -----
>>>>> De: "Brian Goetz" <brian.goetz at oracle.com>
>>>>> À: "Remi Forax" <forax at univ-mlv.fr>, "amber-spec-experts"
>>>>> <amber-spec-experts at openjdk.java.net>
>>>>> Envoyé: Jeudi 17 Août 2017 19:22:21
>>>>> Objet: Re: Condy bsm should be idempotent
>>>>> Can you clarify what you mean by "same"?  According to equals(), or ==?
>>>>>
>>>>> On 8/17/2017 12:15 PM, Remi Forax wrote:
>>>>>> There is a way to solve that, mandate the the BSM of a Condy as to be
>>>>>> idempotent, i.e. a call to a BSM with the same arguments should provide the
> >>>>> same result.