Linking errors with GCJ and SWT

[James Lee]

Hello,

I am trying to compile a simple "Hello, World!" written in Java with
SWT.  The code is as follows:
        
        import org.eclipse.swt.*; 
        import org.eclipse.swt.widgets.*; 
        
        public class HelloWorld { 
                public static void main(String[] args) { 
                        Display display = new Display(); 
                        Shell shell = new Shell(display); 
        
                        Label label = new Label(shell, SWT.NONE); 
                        label.setText("Hello, World!"); 
                        label.pack(); 
        
                        shell.pack(); 
                        shell.open(); 
                        while (!shell.isDisposed()) 
                                if (!display.readAndDispatch()) 
                                        display.sleep(); 
                        display.dispose(); 
                } 
        }

Compiling it with javac and running it with Sun's java works just fine,
however my initial attraction to SWT was the fact that it could be
compiled natively using GCJ. I have had relatively good experiences with
GCJ in the past with both non-GUI and java-gnome programs. Unfortunately
it's just not working out for me this time. I have installed SWT using
Portage. The SWT jar is in my classpath so the program compiles with gcj
fine like:

        jlee@thinkpad ~ $ gcj -c HelloWorld.java 
        jlee@thinkpad ~ $

That leaves me with HelloWorld.o Then I have to link it, but it just
won't work. I have specified the location of the SWT library using the
-l option, but I just get the same error:

        jlee@thinkpad ~ $ gcj --main=HelloWorld -lswt-gtk-3106 HelloWorld.o 
        HelloWorld.o(.text+0x1e): In function `HelloWorld::main(JArray<java::lang::String*>*)': 
        : undefined reference to `org::eclipse::swt::widgets::Display::class$' 
        HelloWorld.o(.text+0x2d): In function `HelloWorld::main(JArray<java::lang::String*>*)': 
        : undefined reference to `org::eclipse::swt::widgets::Display::Display()' 
        HelloWorld.o(.text+0x41): In function `HelloWorld::main(JArray<java::lang::String*>*)': 
        : undefined reference to `org::eclipse::swt::widgets::Shell::class$' 
        HelloWorld.o(.text+0x57): In function `HelloWorld::main(JArray<java::lang::String*>*)': 
        : undefined reference to `org::eclipse::swt::widgets::Shell::Shell(org::eclipse::swt::widgets::Display*)' 
        HelloWorld.o(.text+0x6b): In function `HelloWorld::main(JArray<java::lang::String*>*)': 
        : undefined reference to `org::eclipse::swt::widgets::Label::class$' 
        HelloWorld.o(.text+0x89): In function `HelloWorld::main(JArray<java::lang::String*>*)': 
        : undefined reference to `org::eclipse::swt::widgets::Label::Label(org::eclipse::swt::widgets::Composite*, int)' 
        collect2: ld returned 1 exit status 
        jlee@thinkpad ~ $

There are a few swt libraries in /usr/lib:

        /usr/lib/libswt-atk-gtk-3106.so    /usr/lib/libswt-mozilla-gtk-3106.so 
        /usr/lib/libswt-gnome-gtk-3106.so  /usr/lib/libswt-pi-gtk-3106.so 
        /usr/lib/libswt-gtk-3106.so

I have tried every and all of them. I just don't understand. I'd be
happy to provide anymore information. Thanks for the help!

James Lee
jlee23@umbc.edu