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From "Tim Ellison (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HARMONY-100) text/BidiWrapper issue?
Date Fri, 17 Feb 2006 12:31:25 GMT
    [ http://issues.apache.org/jira/browse/HARMONY-100?page=comments#action_12366777 ] 

Tim Ellison commented on HARMONY-100:
-------------------------------------

Vladimir,

Thanks for the observation.  I agree there is a problem here, but I don't agree with your
conclusion.

Looking at
    http://icu.sourceforge.net/apiref/icu4c/ubidi_8h.html#a22
especially the paragraph beginning "Caution: A copy of this pointer...".

and the native code in 
    Java_org_apache_harmony_text_BidiWrapper_ubidi_1setPara

The Harmony code passes in the address of a local variable '_embeddingLevels' which, as you
point out will go out of scope at the end of this function (precisely the case cautioned against).
 If the JNI impl is data-copying then obviously this can lead to subsequent invalid access,
and if the JNI-impl is pinning then GC could move the byte array upon release of the data.

However, I don't see how committing the memory back to the java object helps?  The memory
needs to be stable until the call to Java_org_apache_harmony_text_BidiWrapper_ubidi_1close.
 Right now it is java memory allocated in the BiDiWrapper:

	private static long createUBiDi(char[] text, int textStart,
			byte[] embeddings, int embStart, int paragraphLength, int flags) {
		char[] realText = null;

		byte[] realEmbeddings = null;


I think the solution is to allocate this realEmbeddings memory as OSMemory in Java and pass
the address into the native call, or allocating it as VM static memory within the native code
itself, then freeing it after closing the wrapper.


> text/BidiWrapper issue?
> -----------------------
>
>          Key: HARMONY-100
>          URL: http://issues.apache.org/jira/browse/HARMONY-100
>      Project: Harmony
>         Type: Bug
>     Reporter: Vladimir Gorr

>
> Let's consider the following test:
> import java.text.Bidi;
> public class Test {
> 	public static void main(String[] args) throws Exception {
> 		Bidi bd = new Bidi(new char[] { 's', 's', 's' }, 0, 
> 				new byte[] { (byte) -7,	(byte) -2, (byte) -3 }, 
> 				0, 3, Bidi.DIRECTION_DEFAULT_LEFT_TO_RIGHT);
> 		System.out.println("Expected 7, real " + "     " + bd.getLevelAt(0));
> 	}
> }
> In my opinion the JNI implementation of Bidi (text/BidiWrapper.c file, ubidi_1setPara()
function) contains a potential bug, namely:
> 1. If  the embeddingLevels  argument is not NULL then _embeddingLevels variable is initialized
with the JNI GetByteArrayElements() function;
> 2. ICU function (ubidi_setPara) initializes ICU inner structure and puts the _embeddingLevels
into it;
> 3. If _embeddingLevels pointer is not NULL then the JNI ReleaseByteArrayElements() function
(with 0 as fourth parameter) is called.
>     This function releases the memory (according to JNI specification) the _embeddingLevels
pointer refers to;
> 4. After that ICU inner structure isn't initialized properly. Call of ICU ubidi_getLevels()
function can return incorrect values (see java test above).
> It seems the JNI_COMMIT parameter instead of "0" should be passed to the ReleaseByteArrayElements()
to avoid this problem.
> I'd like to underline the test mentioned above works w/o any issues for Harmony-14 contribution
(although it shouldn't sometimes IMHO).
> Therefore if there are any doubts in my argumentation this issue can be closed as invalid.


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