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

[Timofei Pushkin]

On Thu, 27 Feb 2025 12:23:28 GMT, Timofei Pushkin <tpushkin at openjdk.org> wrote:

>> Timofei Pushkin has updated the pull request incrementally with five additional commits since the last revision:
>> 
>>  - Fix platform-specific issues
>>  - Rewrite crexec on C++
>>  - Change engine options help
>>  - Move engine wrapper into its own files
>>  - Address review comments
>
> src/hotspot/share/include/crlib/crlib.h line 74:
> 
>> 72:   // The extension should have static storage duration. The application is supposed to cast it to
>> 73:   // the actual extension type.
>> 74:   const crlib_extension_t *(*get_extension)(const char *name, size_t size);
> 
> There is no way to get the full list of extensions and configuration options because I don't see why it should be needed. VM only needs to know if a particular extension/option is supported — for that it can call `get_extension`/`can_configure`.
> 
> I was even thinking about removing `can_configure` in favor of returning an appropriate error code from `configure` (its signature would be changed to return `int`) if the key is not supported, but decided not to because that would require preparing a value for it just to be rejected because the key is not supported.

Now there is a way to do this via an API extension

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PR Review Comment: https://git.openjdk.org/crac/pull/207#discussion_r1978929984