can't find referenced class sun.misc.Unsafe

[Lakedaemon]

Since gradle downloaded release 0.19.4,
I get lots of warnings in proGuard about UnSafe, like

Warning: rx.internal.util.unsafe.UnsafeAccess: can't find referenced class sun.misc.Unsafe

And it breaks the building process (too many warnings in proGuard).
As this is a warning, It is fixed in proGuard by ignoring warnings from Rx (but I'm not sure, this should be done) with
-dontwarn rx.internal.util.**

[benjchristensen]

I don't know anything about proGuard so can't comment about it, but the classes that use sun.misc.Unsafe are all restricted to being in rx.internal.util.unsafe and are only used in environments where it exists (so not on Android).

In 0.19.4 they aren't used anywhere at all. They are in the codebase preparatory for 0.20 where there are used to speed things up in environments where OpenJDK/OracleJDK are used.

The gate for checking whether Unsafe can be used is here: https://github.com/Netflix/RxJava/blob/master/rxjava-core/src/main/java/rx/internal/util/unsafe/UnsafeAccess.java#L47

If anything that relies on sun.misc.Unsafe is used without checking this UnsafeAccess class, it is a bug, as it will fail to work on Android or other JVM implementations without sun.misc.Unsafe. We are allowing it to be used though as it permits performance improvements in some use cases.

/cc @mttkay

[mttkay]

Using -dontwarn is perfectly fine here. The reason ProGuard is failing is that it found this class to be reachable from the byte code it processed, but did not find it included in any of the class files that make up the dependency graph. This typically indicates a class path issue which would result in a runtime crash, but here we know that it would never actually reach the missing class thanks to the safe guard.

Like Ben already said, as long as we make sure we don't access it directly, we should be good.

[chucknthem]

I'm running into this issue with compiling RxJava as part of an android project using buck.

My current work around is adding a dummy Unsafe.java class https://gist.github.com/chucknthem/c3803a299d1d7c384348

And then modifying UnsafeAccess.isUnsafeAvailable() to always return false.

Would be great to include a workaround that compiles in RxJava so we don't have to do this every time we upgrade.

[benjchristensen]

I don't understand what "buck" is. I assume it is this => http://facebook.github.io/buck/ ?

Have you found a code path that actually tries to use sun.misc.Unsafe (a problem that needs to be fixed if so), or this is another tool that does reflection and incorrectly assumes sun.misc.Unsafe is being used (even when it is not being used at runtime)?

[chucknthem]

Thanks for the quick reply.

Yes, that's the correct buck.

False alarm. I got it to compile.

If anyone else is interested, it will compile using java_library buck rule for rxjava-core instead of an android_library which won't include libraries not available in android :)

[benjchristensen]

Thanks for sharing the solution about marking it as a java_library.

[benjchristensen]

Answers for both "proGuard" and "buck" are in the discussion above.