[PATCH] Fix for a JNI bug in CreateJ.cpp (JavaHL)

Dear Subversion Developers:

I attach a patch for a JNI bug. To reproduce the bug, run your JavaHL
regression test under our dynamic JNI bug detector, Jinn
[http://userweb.cs.utexas.edu/~bclee/jinn].

$env JAVA_TOOL_OPTIONS=-agentlib:jinn make check-javahl
...
.Exception in thread "main" xtc.lang.blink.agent.JNIAssertionFailure:
The return type mismatch in CallObjectMethodV: method 0x9626fe4 has
return type: (Ljava/lang/Object;)Z
        at xtc.lang.blink.agent.JNIAssertionFailure.assertFail(JNIAssertionFailure.java:16)
        at org.apache.subversion.javahl.SVNClient.doImport(Native Method)
        at org.apache.subversion.javahl.SVNTests.setUp(SVNTests.java:239)
        at junit.framework.TestCase.runBare(TestCase.java:128)
        at junit.framework.TestResult$1.protect(TestResult.java:106)
        at junit.framework.TestResult.runProtected(TestResult.java:124)
        at junit.framework.TestResult.run(TestResult.java:109)
        at junit.framework.TestCase.run(TestCase.java:120)
        at junit.framework.TestSuite.runTest(TestSuite.java:230)
        at junit.framework.TestSuite.run(TestSuite.java:225)
        at junit.framework.TestSuite.runTest(TestSuite.java:230)
        at junit.framework.TestSuite.run(TestSuite.java:225)
        at junit.textui.TestRunner.doRun(TestRunner.java:121)
        at junit.textui.TestRunner.doRun(TestRunner.java:114)
        at junit.textui.TestRunner.run(TestRunner.java:77)
        at org.apache.subversion.javahl.RunTests.main(RunTests.java:116)
...

To understand what caused the JNI error, I attached a gdb to the JVM.
Relevant caling context and source lines are here.

#5 0x8f86cdf5 in CreateJ::Set (objects=...)
    at subversion/bindings/javahl/native/CreateJ.cpp:912
#6 0x8f86bf4f in CommitMessage::getCommitMessage (this=0x81bf6d0,
    commit_items=0x817ea60)
    at subversion/bindings/javahl/native/CommitMessage.cpp:210
...
#11 0x8f88bff0 in Java_org_apache_subversion_javahl_SVNClient_doImport (
    env=0x805a518, jthis=0xb7281ce4, jpath=0xb7281ce0, jurl=0xb7281cdc,
    jmessage=0x0, jdepth=0xb7281cd4, jnoIgnore=0 '\000',
    jignoreUnknownNodeTypes=0 '\000', jrevpropTable=0x0)
    at subversion/bindings/javahl/native/org_apache_subversion_javahl_SVNClient.cpp:792

In subversion/bindings/javahl/native/CreateJ.cpp
...
   883 jclass clazz = env->FindClass("java/util/HashSet");
...
   895 static jmethodID add_mid = 0;
...
   898 add_mid = env->GetMethodID(clazz, "add", "(Ljava/lang/Object;)Z");
...
   912 env->CallObjectMethod(set, add_mid, jthing);
...

There is a JNI type mismatch between Line 898 and 912.
 The "add_mid" at Line 898 points a Java method returning a boolean
value, but the
 JNI function at Line 912 assumes that "add_mid" is returning a Java reference.
This violates a JNI programming rule:

"You should replace type in Call<type>Method with the Java type of the
method you are calling"
 [http://java.sun.com/javase/6/docs/technotes/guides/jni/spec/functions.html#wp4256]

The fix is trivial and obvious, and line 912 must change its JNI
function from "CallObjectMethod"
to "CallBooleanMethod."

Regards,
Byeong