[crac] RFR: 8365484: [CRaC] Support IgnoreUnrecognizedVMOptions on restore

[Timofei Pushkin]

On Wed, 20 Aug 2025 12:51:25 GMT, Timofei Pushkin <tpushkin at openjdk.org> wrote:

>> src/hotspot/share/runtime/arguments.cpp line 2949:
>> 
>>> 2947:     return false;
>>> 2948:   }
>>> 2949:   if (strcmp(flag.name(), "IgnoreUnrecognizedVMOptions") == 0) {
>> 
>> I see the test is consistent with this, but why do we don't record IgnoreUnrecognizedVMOptions?
>
> Not doing this should not lead to any errors in the current JVM code but I decided to do this because updating `IgnoreUnrecognizedVMOptions` may make the state of the restored VM somewhat inconsistent.
> 
> Suppose `IgnoreUnrecognizedVMOptions` was true on checkpoint and an unrecognized option was used in the command line. Then suppose `IgnoreUnrecognizedVMOptions` was set to false on restore. In such case after restore the command line (which I believe can be read via management or JVM TI) will contain unrecognized options while `IgnoreUnrecognizedVMOptions` will be false.

I actually was not sure if this is needed or not. If you are against this, I'll remove it (i.e. make the option forwardable).

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PR Review Comment: https://git.openjdk.org/crac/pull/263#discussion_r2288071504