[moved here from "multi-bug" 4352424]

Name: yyT116575 Date: 11/27/2000


java version "1.3.0"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.3.0)
Java HotSpot(TM) Client VM (build 1.3.0, mixed mode)


My work is related on ping, traceroute, and nmap function so I implemented all
necessary codes in C and displayed output on screen by using swing component.
In the first step, I tried to just display the result from java part
interactively by using CallVoidMethod() and calling System.out.println().
Everything would be fine for all functions.

Next step, I changed callback method in java part to just call another method,
append(), of JTextArea. The result was VM has been crashed when calling. So I
tried to call the same method directly in native part, C, it seemed work fine
again for ping and nmap only. This solution doesn't work for traceroute.

I also try another way. Traceroute may crash themself, I cut them off from
native code, I means all of them. But I still got the same result. To do next,
I add printf() between every line in C code and java code also to trace where
the problem is. Then I found the problem. The program always crashed while
executing "(*jenv)->CallVoidMethod(jenv,cls,mid,jstr);" because I saw all "in
callback n" where n is 1 until 9 but I never saw 10!

I really need to know the solution for this problem to continue my work.

/* java code */
package trace;
import javax.swing.*;

public class NativeTrace {
        public native String[] doTrace(String host,
                int size,int ttl,int wait,int resolve,JTextArea text);

        public void trace(String host,
                int size,int ttl,int wait,boolean resolve,JTextArea text) {
                int res = 0;
                if (resolve) res = 1;
                String result[] = doTrace(host,size,ttl,wait,res,text);
        }

        static {
                System.loadLibrary("trace");
        }
}


/* snippet C code */
static JNIEnv *jenv;
static jobject jobj;
static jobject jtext;

void callback() {
        if (!jtext) return;
        printf("in callback 6\n");
        cls = (*jenv)->GetObjectClass(jenv,jtext);
        if (cls == 0) {
                fprintf(stderr,"Can't find class javax.swing.JTextArea\n");
                exit(1);
        }

        printf("in callback 7\n");
        mid = (*jenv)->GetMethodID(jenv,cls,"append","(Ljava/lang/String;)V");
        if (mid == 0) {
                fprintf(stderr,"Can't find method append\n");
                exit(1);
        }

        printf("in callback 8\n");
        jstr = (*jenv)->NewStringUTF(jenv,buf);
        printf("in callback 9 %d %d %d %d\n",
                        (int)jenv,(int)cls,(int)mid,(int)jstr);
        (*jenv)->CallVoidMethod(jenv,cls,mid,jstr);
        printf("in callback 10\n");
}

JNIEXPORT jobjectArray JNICALL Java_trace_NativeTrace_doTrace
  (JNIEnv * env, jobject obj, jstring jhost,
   jint size, jint ttl, jint wait, jint resolve, jobject text)
{
        callback("158.108.33.65",1,1.0,0,3);
        return NULL;
}

#
# HotSpot Virtual Machine Error, Unexpected Signal 11
# Please report this error at
# http://java.sun.com/cgi-bin/bugreport.cgi
#
# Error ID: 4F533F4C494E55580E43505005BC
#
# Problematic Thread: prio=1 tid=0x810dc50 nid=0x714f runnable
#
(Review ID: 112817)