RFR: JDK-8216558: Lookup.unreflectSetter(Field) fails to throw IllegalAccessException for final fields

[Remi Forax]

----- Mail original -----
> De: "David Holmes" <david.holmes at oracle.com>
> À: "Adam Farley8" <adam.farley at uk.ibm.com>, "core-libs-dev" <core-libs-dev at openjdk.java.net>
> Envoyé: Vendredi 11 Janvier 2019 14:02:06
> Objet: Re: RFR: JDK-8216558: Lookup.unreflectSetter(Field) fails to throw IllegalAccessException for final fields

> On 11/01/2019 10:46 pm, Adam Farley8 wrote:
>> Hi All,
>> 
>> I posit that you shouldn't be able to change the contents of a a final
>> field.
> 
> Nice in theory, but not true in practice.
> 
>> However, if you use Field.setAccessible(true) before calling
>> Lookup.unreflectSetter(Field), then you can get a MethodHandle that allows
>> you to set the (reflected) value of a static final field.
>> 
>> This seems wrong to me, so here's a change to fix it.
> 
> See:
> 
> https://docs.oracle.com/javase/10/docs/api/java/lang/reflect/Field.html#set(java.lang.Object,java.lang.Object)
> 
> "If the underlying field is final, the method throws an
> IllegalAccessException unless setAccessible(true) has succeeded for this
> Field object and the field is non-static. Setting a final field in this
> way is meaningful only during deserialization or reconstruction of
> instances of classes with blank final fields, before they are made
> available for access by other parts of a program. Use in any other
> context may have unpredictable effects, including cases in which other
> parts of a program continue to use the original value of this field. "
> 
> the same semantics are supported by MH/VH.

No VH doesn't support setAccessible (don't ask me why) ...

> 
> But note this requires the field to be non-static - if you can set a
> static final field this way then that may be a bug (they can still be
> set via native methods of course).
> 
> David

Rémi

> -----
> 
>> webrev: http://cr.openjdk.java.net/~afarley/8216558/webrev/
>> bug: https://bugs.openjdk.java.net/browse/JDK-8216558
>> 
>> Opinions invited.
>> 
>> Best Regards
>> 
>> Adam Farley
>> IBM Runtimes
>> 
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