On Thu, 23 Feb 2023 08:32:29 GMT, Claes Redestad <redes...@openjdk.org> wrote:
>> `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.
Scratch that: as it seems to be important that we don't switch after startup
then what this code is really reaching for is `static final` field semantics.
Since `StandardCharsets` might be loaded very early a holder class pattern
might be necessary:
isGB18030_2000() { return GB18030Properties.GB18030_2000; }
private static class GB18030Properties {
private static final GB18030_2000 = init();
private static boolean init() {
if (VM.initLevel() < 1) {
// Cannot get the system property yet. Assumes non-2000
return false;
}
return
"2000".equals(GetPropertyAction.privilegedGetProperty("jdk.charset.GB18030"));
}
}
-------------
PR: https://git.openjdk.org/jdk/pull/12518
