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GeezerVison is showing github.com — Using Custom Comparator throws NullPointerException after GC · Issue #125 · lmdbjava/lmdbjava

Using Custom Comparator throws NullPointerException after GC #125

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Using Custom Comparator throws NullPointerException after GC#125
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bugAn issue relates to behaviour that violates the intention of the libraryAn issue relates to behaviour that violates the intention of the library

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@jheister
jheister
opened on Apr 6, 2019
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When a Dbi is created using a custom comparator it only works whilst a full GC has not run. This can be show by adding a System.gc() between the construction of the map and the put invocation in org.lmdbjava.DbiTest#customComparator.

On executing put it throws:
java.lang.NullPointerException: callable is null at jnr.ffi.provider.jffi.NativeClosureProxy.getCallable(NativeClosureProxy.java:57) at jnr.ffi.provider.jffi.NativeClosureProxy$$impl$$0.invoke(Unknown Source) at com.kenai.jffi.Foreign.invokeL5(Native Method) at com.kenai.jffi.Invoker.invokeL5(Invoker.java:438) at org.lmdbjava.Library$Lmdb$jnr$ffi$0.mdb_put(Unknown Source) at org.lmdbjava.Dbi.put(Dbi.java:421)

This happens since NativeClosureFactory.ClosureReference is a WeakReference and nothing else holds a reference to theComparatorCallback.

I've tested that converting ComparatorCallback ccb into a field fixes this, since it ensures the callback remains alive whilst the Dbi object is accessible.

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  1. bp-alex
    added
    bugAn issue relates to behaviour that violates the intention of the libraryAn issue relates to behaviour that violates the intention of the library
    on Apr 9, 2019

  2. bp-alex commented on Apr 9, 2019

    @bp-alex
    bp-alex
    on Apr 9, 2019
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    Thanks for such a well-described issue report. I was able to reproduce it locally, but didn't add the System.gc() to the test because it causes PMD and Spotbugs to object.

    Reacted by Justin Heister
  3. bp-alex
    closed this as completedin 5912bebon Apr 9, 2019
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