Unable to call c++ .so file in java

Question

this is my java file prog1.java
class prog1
     static
          try
               System.loadLibrary("test");
          catch(UnsatisfiedLinkError ule)
               System.out.println(ule);
               //ule.printStackTrace();
     public static native void test();
     public static void main(String args[])
          System.out.println("Hello World!");
          test();
now this is my c++ file prog1.cpp
#include<stdio.h>
#include "prog1.h"
#include<jni.h>
JNIEXPORT void JNICALL Java_prog1_test(JNIEnv *env, jclass jobj)
     printf("Hello world from VC++ DLL\n");
Steps I follow to execute it
1. compile the java code
2. create the header file with javah command
3.compile the c++ code with the command
g++ -c -fPIC -I/usr/local/jdk1.5.0_02/include -I/usr/local/jdk1.5.0_02/include/linux prog1.cpp
4.Now creating the .so file with the command
g++ -shared -O6 -fPIC -I/usr/local/jdk1.5.0_02/include -I/usr/local/jdk1.5.0_02/include/linux -Dlinux -nostdlib -nostartfiles prog1.o -o libtest.so
It generates the error
java.lang.UnsatisfiedLinkError: /root/krgaurav/c++dll/libtest.so: /root/krgaurav/c++dll/libtest.so: undefined symbol: __gxx_personality_v0
Hello World!
Exception in thread "main" java.lang.UnsatisfiedLinkError: test
at prog1.test(Native Method)
at prog1.main(prog1.java:20)
You have new mail in /var/spool/mail/root
Please help .
If I change the file name prog1.cpp to prog1.c it perfectly works .

Answer 1

C++ has a different linkage than C. Function names are changed by the C++ compiler (don't ask me exactly how and why, it's too long ago I was programming in C++, but it's necessary because of certain features of the C++ language).
So if you compile your source as C++, the function names become different from what JNI expects and it won't work.