[Rev 02] RFR: 8246348: Crash in libpango on Ubuntu 20.04 with some unicode chars

[Johan Vos]

On Fri, 12 Jun 2020 14:25:25 GMT, Kevin Rushforth <kcr at openjdk.org> wrote:

>> I don't think it will be `null` but it will be `0` in which case it is stored in the `Map`
>> The only reason the str == null is then that we never tried to convert the Java chars to utf8, unless I'm missing a
>> case?
>
> Oh, right. It will be a Long 0, not null. If you store it you will still have the problem I mentioned with dispose
> unless you add back in the `str != 0` check. And you would need a check for `str != 0` in the layout method so that the
> second time it doesn't treat it as a valid pointer. It might be safer to not store it if 0, which matches the current
> behavior?

That makes sense indeed. For the dispose call, a valid pointer is required.

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PR: https://git.openjdk.java.net/jfx/pull/249