SonarCloud reports multiple incorrect double-checked locking cases in
`sun.java2d.CRenderer`. For example:
Arc2D arcToShape;
...
if (arcToShape == null) {
synchronized (this) {
if (arcToShape == null) {
arcToShape = new Arc2D.Float();
}
}
}
`Arc2D` contains fields that are not `final`. `arcToShape` is not `volatile`.
This makes it an incorrect DCL.
This code is used by Mac OS, do it would probably blow up some time later on M1.
This is the candidate fix that preserves the semantics. I am doing this fix
blindly so far, without testing on real Mac OS. But maybe there is no need to
do any of this, because the setter methods overwrite the contents of all these
objects under their own sync. So, maybe we can just allocate those objects
without DCL-backed caching and pass them in?
-------------
Commit messages:
- JDK-8263467: Incorrect double-checked locking in sun.java2d.CRenderer
Changes: https://git.openjdk.java.net/jdk/pull/2948/files
Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=2948&range=00
Issue: https://bugs.openjdk.java.net/browse/JDK-8263467
Stats: 50 lines in 1 file changed: 15 ins; 0 del; 35 mod
Patch: https://git.openjdk.java.net/jdk/pull/2948.diff
Fetch: git fetch https://git.openjdk.java.net/jdk pull/2948/head:pull/2948
PR: https://git.openjdk.java.net/jdk/pull/2948
