@related: [[Java]] [[gcc]] [[Compiler]] [[TuxGuitar]] [[jdk]]


==== [[Libre]] [[Java]] [[Compiler]] : gcj ====

  * http://gcc.gnu.org/java
  * irc://irc.oftc.net/#gcj
  * irc://irc.freenode.net/#classpath.

[[ToDo]] : http://lists.debian.org/debian-gcc/2005/04/msg00020.html

<code>
  mkdir -p gcjtest ; cd gcjtest
  cat > Test.java << EOF
  class Test {
   public static int f(int in) {
       System.out.println("#{ Test.java::f");
       System.out.println("#" + in );
       System.out.println("#} Test.java::f");
       return in;
   }
   // public static void fvoid() { } // jni bug to check?
  }
EOF

  cat > Main.java <<EOF
  class Main {
   public static void main(String[[]] args) {
       System.out.println("#{ Main.java::main");
       Test.f ( args.length );
       System.out.println("#} Main.java::main");
   }
  }
EOF
</code>


On [[Linux]] :

  # $ make
  gcj -C --classpath=. Test.java
  gcj -c  -o Test.o --classpath=. Test.java
  libtool --mode=link --tag=GCJ gcj --shared Test.o  -o libgcjtest.so
  gcj -c  -o Main.o --classpath=. Main.java
  gcj -o main --main=Main --classpath=. Main.o -lgcjtest -L. -lgcj

  ldd main
  #       libgcjtest.so => ./libgcjtest.so (0xb7fe7000)
  #       libgcj.so.3 => /usr/lib/./libgcj.so.3 (0xb79f4000)
  #       libgcc_s.so.1 => /lib/libgcc_s.so.1 (0xb79d8000)
  #       libm.so.6 => /lib/tls/libm.so.6 (0xb79b6000)
  #       libpthread.so.0 => /lib/tls/libpthread.so.0 (0xb79a7000)
  #       libz.so.1 => /usr/lib/./libz.so.1 (0xb7995000)
  #       libdl.so.2 => /lib/tls/libdl.so.2 (0xb7992000)
  #       libc.so.6 => /lib/tls/libc.so.6 (0xb785d000)
  #       /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0xb7fea000)

  LD_LIBRARY_PATH=. && ./main *
  #{ Main.java::main
  #{ Test.java::f
  #7
  #} Test.java::f
  #} Main.java::main

==== On [[Cygwin]] : ====

  gcj -C --classpath=. Test.java
  gcj -c  -o Test.o --classpath=. Test.java
  gcj -Wl,-Bsymbolic -shared -fPIC -fjni -findirect-dispatch Test.o  -o libgcjtest.so # ok [[Cygwin]]
  gcj -c  -o Main.o --classpath=. Main.java
  gcj -o main --main=Main --classpath=. Main.o -lgcjtest -L. -lgcj
  # h:\usr\local\WIN32\opt\thisiscool-gcc\gcc-3.4\bin\..\lib\gcc\i686-pc-mingw32\3.4.0\..\..\..\..\i686-pc-mingw32\bin\ld.exe:
  # cannot find -lgcjtest

http://www.thisiscool.com/gcc_mingw.htm


gcj works pretty fine, unless when I tried to make a shared library (.so) under
[[Cygwin]], this code works flawlessly w/ gcc 3.4 [[Linux]] [[Debian]]

you wrote a warning on gcc 4.0 but this also happend on 3.4 (see code)


==== [[C++]] ====

http://gcc.gnu.org/onlinedocs/gcj/Invocation.html#Invocation

<code>
  cat > main-cpp.cpp << EOF
  #include <gcj/cni.h>
  #include <java/lang/System.h>
  #include <java/io/PrintStream.h>
  #include <java/lang/Throwable.h>

  int main(int argc, char *argv) {
       using namespace java::lang;

       try {
         JvCreateJavaVM(NULL);
         JvAttachCurrentThread(NULL, NULL);

         String *message = JvNewStringLatin1("Hello from C++");
         JvInitClass(&System::class$);
         System::out->println(message);

         JvDetachCurrentThread();
       } catch (Throwable *t) {
         System::err->println(JvNewStringLatin1("Unhandled Java exception:"));
         t->printStackTrace();
       }
     }
EOF
</code>

  make CXX=gcj LDFLAGS=-lgcj main-cpp  && ./main-cpp

==== [[C++]] call a dynamic native [[Java]] library ====

<code>
  cat > main-test-cpp.cpp << EOF
  #include <gcj/cni.h>
  #include <java/lang/System.h>
  #include <java/io/PrintStream.h>
  #include <java/lang/Throwable.h>
  #include "Test.h"

  int main(int argc, char *argv) {
       using namespace java::lang;

       try {
         JvCreateJavaVM(NULL);
         JvAttachCurrentThread(NULL, NULL);

         String *message = JvNewStringLatin1("Hello from C++");
         JvInitClass(&System::class$);
         System::out->println(message);

        ::Test::f( argc );

        JvDetachCurrentThread();
       } catch (Throwable *t) {
         System::err->println(JvNewStringLatin1("Unhandled Java exception:"));
         t->printStackTrace();
       }
     }
EOF
</code>

  make CXX=gcj LDFLAGS="-lgcj -lgcjtest -L." main-test-cpp  && ./main-test-cpp *

  Hello from C++
  #{ Test.java::f
  #10
  #} Test.java::f


  ldd main-test-cpp
        libgcj.so.3 => /usr/lib/libgcj.so.3 (0xb79e4000)
        libgcjtest.so => ./libgcjtest.so (0xb79e1000)
        libgcc_s.so.1 => /lib/libgcc_s.so.1 (0xb79d8000)
        libm.so.6 => /lib/tls/libm.so.6 (0xb79b6000)
        libpthread.so.0 => /lib/tls/libpthread.so.0 (0xb79a7000)
        libz.so.1 => /usr/lib/libz.so.1 (0xb7995000)
        libdl.so.2 => /lib/tls/libdl.so.2 (0xb7992000)
        libc.so.6 => /lib/tls/libc.so.6 (0xb785d000)
        /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0xb7fea000)


==== GCJH ====

<code>
cat Test.java
class Test
{
    static final String FILE = new String("Test.java");

    public static void test()
    {
        System.out.println( FILE + ":0: log: #{ " + "Test::test");
        System.out.println( FILE + ":0: log: #} " + "Test::test");
    }

    public static void main(String[] args)
    {
        System.out.println( FILE + ":0: log: #{ " + "Test::main");
        test();
        System.out.println( FILE + ":0: log: #} " + "Test::main");
    }

}
gcj -c  -o Test.class.o --classpath=. Test.java
libtool --mode=link --tag=GCJ gcj --shared  -o libTest.jar.so Test.class.o
libtool: link: gcj --shared -o libTest.jar.so Test.class.o 
javac Test.java
gcjh Test.class -o Test.java.h
cat Test.java.h

// DO NOT EDIT THIS FILE - it is machine generated -*- c++ -*-

#ifndef __Test__
#define __Test__

#pragma interface

#include <java/lang/Object.h>
#include <gcj/array.h>

extern "Java"
{
    class Test;
}

class Test : public ::java::lang::Object
{

public: // actually package-private
  Test();
public:
  static void test();
  static void main(JArray< ::java::lang::String * > *);
public: // actually package-private
  static ::java::lang::String * FILE;
public:
  static ::java::lang::Class class$;
};

#endif // __Test__
cat main.cpp
#include <gcj/cni.h>
#include <java/lang/System.h>
#include <java/io/PrintStream.h>
#include <java/lang/Throwable.h>
#include "Test.java.h"

int main(int argc, char *argv[])
{
  using namespace java::lang;

  try {
    JvCreateJavaVM(NULL);
    JvAttachCurrentThread(NULL, NULL);

    String *message = JvNewStringLatin1( __FILE__ ":" "0" ": log:" );
    JvInitClass(&System::class$);
    System::out->println(message);

    ::Test::test();

    //::Test::main();

    JvDetachCurrentThread();
  } catch (Throwable *t) {
    System::err->println(JvNewStringLatin1("Unhandled Java exception:"));
    t->printStackTrace();
  }
}
gcj -L. -lgcj -lTest.jar -o main.exe main.cpp
cc1plus: warning: command line option "-fbootclasspath=./:/usr/share/java/libgcj-4.4.jar" is valid for Java but not for C++
LD_LIBRARY_PATH=. ./main.exe
main.cpp:0: log:
Test.java:0: log: #{ Test::test
Test.java:0: log: #} Test::test
</code>