[kaffe] JNI under ARM

[Patrick McNeil]

This is the C code:

#include "stdafx.h"
#include <stdlib.h>
#include "../cphidget.h"
#include "phidget_jni.h"
#include <stdio.h>

jclass ph_exception_class;
jmethodID ph_exception_cons;
JavaVM *ph_vm = 0;

jint JNICALL
JNI_OnLoad(JavaVM *vm, void *reserved)
{
	JNIEnv *env;
	jint version = 0;

	ph_vm = vm;
	if ((*vm)->AttachCurrentThread(vm, (void **)&env, NULL))
	{
		WARN("Couldn't Attach Thread");
		(*env)->ExceptionDescribe(env);
		(*env)->ExceptionClear(env);
		abort();
	}
	
	if(!(version = (*env)->GetVersion(env)))
	{
		WARN("Couldn't get version");
		(*env)->ExceptionDescribe(env);
		(*env)->ExceptionClear(env);
		abort();
	}
	WARN("JNI Version: %08x",version);

	if (!(ph_exception_class = (*env)->FindClass(env,
	  "com/phidgets/PhidgetException")))
	{
		WARN("Coulnd't find class \"com/phidgets/PhidgetException\"");
		(*env)->ExceptionDescribe(env);
		(*env)->ExceptionClear(env);
		abort();
//***** This is where is fails *****//
	}

	if (!(ph_exception_class = (jclass)(*env)->NewGlobalRef(env,
	  ph_exception_class)))
	{
		WARN("Couldn't create global ref ph_exception_class");
		(*env)->ExceptionDescribe(env);
		(*env)->ExceptionClear(env);
		abort();
	}
	if (!(ph_exception_cons = (*env)->GetMethodID(env,  
ph_exception_class, "<init>",
	  "(ILjava/lang/String;)V")))
	{
		WARN("Coulnd't get Method ID for init in ph_exception_class");
		(*env)->ExceptionDescribe(env);
		(*env)->ExceptionClear(env);
		abort();
	}

	return JNI_VERSION_1_2;
}

And this is the java code that invokes it:

public class Phidget
{
	static {
		System.loadLibrary("phidget21");
	}
	......
}

It never makes it out of the C function JNI_OnLoad, and either aborts  
(explicitly), of seg faults before it gets to the abort call in the  
findClass failure path. The exception is nullpointerexception if i  
get a chance to read it. I've been working with gdb embedded on the  
arm to try and resolve the issues but I'm just not very familiar with  
the kaffe sources.

On a side note - where can I put my .jar that contains the libraries  
needed by JNI in C to get them to load properly? I've had to place  
phidgets.jar in the same directory as rt.jar just to get kaffe to see  
it from C. Adding it to the CLASSPATH doean't seem to work (on ARM or  
the debian PC).

Thanks for any advice

-Patrick


On 11-Sep-06, at 9:23 AM, Dalibor Topic wrote:

> Patrick McNeil wrote:
>
>> Hi,
>>
>> I have kaffe compiled and working under ARM9, but I'm running  
>> into  troubles with JNI. Incidentally, I'm having these same  
>> problems with  the default kaffe install on my Debian PC.  
>> Basically, calling  findclass in the c library causes a seg fault,  
>> on a  null pointer  exception. This is code that works fine under  
>> Sun JRE on the same box  so... I just wondering if this is a known  
>> issue, and if there is a fix?
>
> Hi Patrick,
>
> could you post a short example that shows the bug?
>
> cheers,
> dalibor topic