Can @Stable (or something similar) be made accessible? (original) (raw)

Peter Levart peter.levart at gmail.com
Fri Jan 12 11:35:39 UTC 2018

Hi Andrew,

On 01/12/2018 09:47 AM, Andrew Haley wrote:

On 12/01/18 04:33, Jason Greene wrote:

The internal @Stable facility provides the desired semantics and precision, but it is heavily locked down, with privileged code checks and export restrictions. Could this be made more accessible (or perhaps a variant restricted to just final fields)? Informing the compiler that a final field is a true lazy initialized constant, with no store-to-final seems a pretty useful construct in general. I can understand that the long term desire is that this shouldn’t be necessary, and should be inferred [3], but at that point the annotation is still useful as documentation and legacy compatibility. If nothing else could it be allowed in non-privileged code via some flag? I don't know of any way to do that without compromising the integrity of the JVM. All that anybody would have to do to break the VM is to define a field as @Stable and then change the field.

Would you be so kind to explain how this breakage occurs? I can understand that improper use of @Stable annotation may break the intended semantics of a program, but to break the integrity of VM? I'm trying to imagine the scenario, but can't.

Regards, Peter

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