Re: GCJ and C++ (calling Java from C++)

[Lothar Werzinger <lothar at tradescape dot biz>]

On Tuesday 29 November 2005 09:42, Andrew Haley wrote:
> The first thing in Section 12.15, Invocation, is:
>
> Function: jint JvCreateJavaVM (JvVMInitArgs* VM_ARGS)
>      Initializes the Java runtime
>
> Did you call that?
>
> Did you do everything in 12.15.2, Example?

Well it seems you did not get a chance to look at the example I attached in 
the first mail. However to make things short, this is the code I use:

  try
  {
    // create the virtual machine
    JvCreateJavaVM(NULL);
    JvAttachCurrentThread(NULL, NULL);
    cout << "created VM" << endl;
    
    String *fileName = JvNewStringLatin1("My.extlibrary");

    JvInitClass(&System::class$);
    System::out->println(fileName);
    
    LibraryTest * p_libraryTest = LibraryTest::makelibrary(fileName);
    
    LibraryTest::printlibrary(p_libraryTest);
    
    JvInitClass(&LibraryTest::class$);

    Library * p_library = p_libraryTest->getlibrary();
    cout << "p_library=" << hex << p_library << endl;

    JvInitClass(&Library::class$);

    EList * p_books = p_library->getBooks();
    cout << "p_books=" << hex << p_books << endl;
    
    JvDetachCurrentThread();
  }
  catch (Throwable *t)
  {
    System::err->println(JvNewStringLatin1("Unhandled Java exception:"));
    t->printStackTrace();
  }

> That's fine.  But first, we will try the simple things, then the hard
> things.
 I also get the correct output for the cout and the java println:
     [exec] created VM
     [exec] My.extlibrary

I even get the (lengthy and thus omitted) output from the call to the static 
LibraryTest::printlibrary(p_libraryTest); call.

I get the exception when I call p_library->getBooks();

I also tried to move the JvInitClass(&Library::class$); call above the 
p_libraryTest->getlibrary(); call, but the the p_libraryTest->getlibrary(); 
call fails with this exception.

     [exec] Unhandled Java exception:
     [exec] java.lang.LinkageError: unexpected exception during linking: 
org.eclipse.emf.examples.extlibrary.Library
     [exec] at java.lang.VMClassLoader.transformException(java.lang.Class, 
java.lang.Throwable) (/usr/lib64/libgcj.so.6.0.0)
     [exec] at java.lang.VMClassLoader.resolveClass(java.lang.Class) 
(/usr/lib64/libgcj.so.6.0.0)
     [exec] at java.lang.Class.initializeClass() (/usr/lib64/libgcj.so.6.0.0)
     [exec] at .JvInitClass(java.lang.Class) 
(/usr/include/c++/4.0.2/gcj/cni.h:31)
     [exec] at .main 
(/home/lothar/workspace/org.eclipse.emf.examples.library.edit/cpp/librarytest/main.cpp:103)
     [exec] at .__libc_start_main (/lib64/tls/libc-2.3.5.so)
     [exec] Caused by: java.lang.NullPointerException
     [exec] at java.lang.VMClassLoader.resolveClass(java.lang.Class) 
(/usr/lib64/libgcj.so.6.0.0)
     [exec] ...4 more

So I am a kind of stuck here :-(

> Andrew.
Lothar
-- 
Lothar Werzinger Dipl.-Ing. Univ.
framework & platform architect
Tradescape Inc.
111 West St. John Street, Suite 200
San Jose, Ca 95113
email: lothar@tradescape.biz