Re: gcj: issue with run time library loading

[David Daney <ddaney at caviumnetworks dot com>]

Vaijayanthi Mala Suresh wrote:
> Hi,
>
> I am trying to use JNI calls using gcj.
>
> Hello.java is the jave code having a native method.
>
> gcj -c -fjni Hello.java -o MyApp.o
> gcjh Hello -o MyApp.h
> ar -rcs libHello.a MyApp.o
>
> Hello.c contains the native code implementation
> gcjh -jni Hello
> g++ -c Hello.c
> ar rcs libNative.a Hello.o
>
>
> I have a test.cpp where I have initialized the JVM and I am trying to
> invoke a method in the Java code which inturn invokes the native
> method. I have linked the above libraries along with test.o
>
> I am getting the following error
>
> Unhandled Java exception:
> java.lang.UnsatisfiedLinkError: natPrint
>    <<No stacktrace available>>
>
> Can anyone help me to resolve this problem.

JNI under gcj is just like JNI under Sun/OpenJDK.  The JNI library must 
be compiled as a shared object.

Something like this:

g++ -fPIC -c Hello.c
g++ -shared -o Hello.so Hello.o

Then of course you need to use java.lang.System.loadLibrary() to load 
the library before calling any methods in it.

You will note that these are the *exact* same steps you would take if 
you were to use the library on Sun's JDK.  You wouldn't even have to 
recompile the library.

David Daney