Java callback from C

Question

I'm trying to call Java class method from C code (via JNI), but Java VM dies with
# An unexpected error has been detected by HotSpot Virtual Machine:
#  EXCEPTION_ACCESS_VIOLATION (0xc0000005) at pc=0x6d6c79dd, pid=128, tid=2192
# Java VM: Java HotSpot(TM) Client VM (1.5.0_11-b03 mixed mode)
# Problematic frame:
# V  [jvm.dll+0x879dd]
# An error report file with more information is saved as hs_err_pid128.log
# If you would like to submit a bug report, please visit:
#   http://java.sun.com/webapps/bugreport/crash.jsp
Hello world!
Hello world, from Java to C!This is Java code:
Hello.java
class Hello
     public native void sayHello();
     public native void sayHello(String hello);
     public native void sayHello(Callback callback);
     static
          try
               System.loadLibrary("hello");
          catch(Exception e)
               System.out.println("exception " + e.getMessage());
     public static void main(String[] args)
          Hello h = new Hello();
          h.sayHello ();
          h.sayHello("Hello world, from Java to C!");
          Callback callback = new Callback();
          h.sayHello(callback);
}Callback.java
public class Callback
     public void sayHello(int num)
          for(int i=0; i<num; i++)
               System.out.println("Hello world, from C to Java!");
}This is C code:
Hello.c
#include <mingw/_mingw.h> //because there are some types needed for JNI
#include <jni.h>
#include "Hello.h"
#include <stdio.h>
JNIEXPORT void JNICALL Java_Hello_sayHello__
  (JNIEnv *env, jobject obj)
     printf("Hello world!\n");
     return;
JNIEXPORT void JNICALL Java_Hello_sayHello__Ljava_lang_String_2
  (JNIEnv *env, jobject obj, jstring hello)
     const char *str = (*env)->GetStringUTFChars(env, hello, 0);
     printf("%s", str);
     (*env)->ReleaseStringUTFChars(env, hello, str);
     return;
JNIEXPORT void JNICALL Java_Hello_sayHello__LCallback_2
  (JNIEnv *env, jobject obj, jobject call)
     jclass clazz = (*env)->GetObjectClass(env, call);
     jmethodID id = (*env)->GetMethodID(env, clazz, "sayHello", "(I)V");
     if(id == NULL)
          //(*env)->ExceptionDescribe(env);
          (*env)->ExceptionClear(env);
          printf("Method not found!\n");
}C if linked with
gcc -mno-cygwin -Wl,--add-stdcall-alias,--kill-at -shared -Wl,--output-def=Hello.def -o"hello.dll"  ./Hello.oand 'def' file is:
EXPORTS
Java_Hello_sayHello__
Java_Hello_sayHello__Ljava_lang_String_2
Java_Hello_sayHello__LCallback_2I can't see what am I doing wrong, but I'm sure thats something plain that I'm missing. Code is compiled with latest Cygwin in Eclipse 3.2.2 under WinXP OS. It is runned under jre1.5.0_11.
Any help is appreciated. Thanks.

Answer 1

Now I commented two calls for printing on screen in C code, and left just callback call, and same error is still there:
# An unexpected error has been detected by HotSpot Virtual Machine:
#  EXCEPTION_ACCESS_VIOLATION (0xc0000005) at pc=0x6d6c79dd, pid=3656, tid=3660
# Java VM: Java HotSpot(TM) Client VM (1.5.0_11-b03 mixed mode)
# Problematic frame:
# V  [jvm.dll+0x879dd]
# An error report file with more information is saved as hs_err_pid3656.log
# If you would like to submit a bug report, please visit:
#   http://java.sun.com/webapps/bugreport/crash.jsp
#Can anyone tell me what does this mean (or how to fix my code)?
Thank you for your reply.