<i18n dev> RFR: 8301119: Support for GB18030-2022 [v2]

[Claes Redestad]

On Wed, 22 Feb 2023 17:52:01 GMT, Naoto Sato <naoto at openjdk.org> wrote:

>>> curious - what scenario triggers this call at initLevel < 1 ?
>> 
>> It's not supported, but it is possible that someone might run with -Dfile.encoding=GB18030, in which case the default charset is used before the system properties are initialized in initPhase1. Checking the init level breaks the circularity, the only downside is that can't switch to GB18030-2000 at the same time.
>
> `Charset` class is initialized *before* system properties are set up, in order to check the JNU encoding (used for file path name) is a supported charset or not. In some OS environments, GB18030 is the native encoding so we need to avoid checking the system property in such a case.

`@Stable` semantics are still fuzzy to me but the rule I've adhered to is that back to back stores to the field - if unavoidable - needs to be idempotent since the JIT (or AOT) may record any non-null value as a compile time constant at any time.

I'd write this to not update the static field if initLevel() < 1. Such calls should be rare and only happen once on a system that has GB18030 as their native encoding.

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PR: https://git.openjdk.org/jdk/pull/12518