[crac] RFR: 8350845: [CRaC] Support C/R engines in form of a library [v2]

[Timofei Pushkin]

On Wed, 5 Mar 2025 09:11:45 GMT, Radim Vansa <rvansa at openjdk.org> wrote:

>> Not always, for example an engine can interpret `--XX:CRaCEngineOptions=args=--arg1 --XX:CRaCEngineOptions=args=--arg2` as `--XX:CRaCEngineOptions=args="--arg1 --arg2"` (i.e. concatenate all `args` into a single string), so it is up to the engine implementation to issue a warning.
>> 
>> I can implement such warning in crexec but that would require keeping track of whether each option has been set or not (not a problem to implement, just that it'll stay in the configuration even after the parsing is done).
>
> The engine is not interpreting JVM options; engine receives its programmatic configuration and has to deal with that. JVM defines the user API and we can decide that repeated use of the same argument is prohibited (as that would be more likely an user error).

I mean that an engine can interpret reconfiguration of the same key not as overwriting of the previous value but somehow differently, e.g. as concatenation in my example. Since the VM is just passing the keys through I would leave the interpretation up to the engine. But it's not a strong opinion, I can move the warning to JVM if you still think it would be better.

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PR Review Comment: https://git.openjdk.org/crac/pull/207#discussion_r1981029557