[Rev 01] RFR: 8246348: Crash in libpango on Ubuntu 20.04 with some unicode chars

[Kevin Rushforth]

On Fri, 12 Jun 2020 14:16:06 GMT, Johan Vos <jvos at openjdk.org> wrote:

>> If `str` is null, you would end up retrying it anyway, since `Map::get` will return `null` the next time (if there is a
>> next time). Also, I think the dispose method might then crash trying to free a null pointer. So I think Phil is right
>> and that you should not add the `str` to the `Map` if it is null.
>
> 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?

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