Need to delete local references in unknown calling context

Hi,
I was looking for the need to delete local references and came across this documentation,
What does unknown caller context mean? and how does it cause local references to remain allocated in reference table although the native function returns?
http://java.sun.com/docs/books/jni/html/refs.html
5.2.1 Freeing Local References
You want to write a utility function that is called from unknown contexts. The MyNewString example shown in Section 4.3 illustrates the use of Delete-LocalRef to delete promptly local references in a utility function. Otherwise there will be two local references that remains allocated after each call to the MyNewString function.

how does it cause local references to remain allocated in reference table although the native function returns?Because it doesn't return to the JVM where it gets deallocated, it returns to the unknown caller context, i.e. some other piece of native code in your JNI layer. So the references remain until the unknown caller context returns to the JVM.

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==============
// JNITest.java
interface INativeNotification
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static DWORD dwThreadId;
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BOOL APIENTRY DllMain( HANDLE hModule,
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Hi,
First of all, thank you for your time and interest.
Let me first recapitulate the history of this problem :
We have a C interface for controlling our HW boards. A few years ago, we wrote a java interface for one of our customers. This JNI wrapper was certified for the SUN JRE and has been used for several years now without a problem. There are several java and native callback functions in this wrapper and our development team took some design decisions (e.g. no DeleteLocalRef's, re-fetching the jclass and methodID in the callback functions, ...).
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However, when we look in the IBM JVM diagnostics guide (Chapter 6 : Understanding the Java Native Interface, see http://www-106.ibm.com/developerworks/java/jdk/diagnosis/), they provide the following code as a sample for loosing local references, resulting in the underlying object being garbage collected.
jobject myJNIfunc1 ()
return env->NewObject ();
void myJNIfunc2 ()
jobject obj;
obj = myJNIfunc1 ();
.. -> no local reference to obj exists, and the garbage collector can collect it
Are we interpreting the IBM JVM diagnostics guide wrong or is there a problem in the IBM JVM ?
The SUN JVM deletes the local references properly.

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Message Edited by david_jenkinson on 06-11-2007 05:07 PM
Attachments:
step reference specify module.png ‏25 KB

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Need to delete local references in unknown calling context

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