Create JavaRef, JavaLocalRef, and JavaGlobalRef to hold references and manage memory #124
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Conceptually, this looks good. I'd like it if we could run tests for Spark.jl and Taro.jl on this branch, since those two package exercise the JVM much more than JavaCall tests can. |
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I just checked Taro.jl. The tests run well against this branch. The one issue is that I had to add write permissions to |
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I cannot get Spark.jl to work on Linux with Julia 1.3.1 to Julia 1.5-beta1 on Linux. I created an issue here: |
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| Pkg.test("Taro") | ||
| #include(joinpath(dirname(dirname(pathof(Taro))),"test","runtests.jl")) | ||
| try |
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Can't we add it as a test depedency?
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I added Taro as a test dependency by putting it in extras.
However, Taro is failing to work on Mac and this does not appear to be caused by this PR.
| [extras] | ||
| Pkg = "44cfe95a-1eb2-52ea-b672-e2afdf69b78f" | ||
| Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40" | ||
| Taro = "61d0e4fa-4e73-5030-88a9-ae4c27b203dd" |
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@aviks I added Taro as a test dependency on this like as an "extra".
Background: Local and Global Java References
Currently all Java references to objects in JavaCall are "local" Java references for variables that are only meant to live the lifetime of a Java method call after which the Java garbage collector may free the underlying memory. Because the use of these references in JavaCall is occurring outside of the context of a Java method call, currently the local references are never marked for garbage collection. The local part of a Java method call can emulated by the use of
JNI.PopLocalFrameandJNI.PushLocalFrame.However, there are some are some references that we would not like to mark for collection, notably the metaclasses. The JNI also has the concept of global references that are meant to survive a Java method call.
JavaRef, JavaLocalRef, JavaGlobalRef, and JavaNullRef types
To improve memory management, I create a new family of types,
JavaRefwithJavaLocalRefandJavaGlobalRefsubtypes to track the scope of the underlying references. This also helps us to provide the correct deletion procedure for the references. Additionally, I create aJavaNullReftype and a constantJ_NULLto track null or deleted references.JProxy
This also permits advancement of #91 and #112 . JProxy makes some alterations to core JavaCall.jl to introduce global references. This is an alternative design that allows for both local and global references. We will thus backout the changes in to core JavaCall in #112 and use this Java reference management design instead.
Technical Notes
To facilitate easy extraction of the
Ptr{Nothing}to pass to the JNI viaccallI overloadedPtrto replace the reference to the.ptrfield of JavaObject.Pending
For many JNI calls, it would be nice to simply pass the
JavaObjectrather than having to callPtr. To allow this, I plan on creating an abstract type in the JNI module. Concrete derivatives of that abstract type then should implement theBase.convertorBase.cconvertmethods to convert the concrete type toPtr{Nothing}. This would allow us to maintain the independence of theJNImodule while allowing for alternate implementations.