Re: Will cni be the sane native interface to c++ in openjdk U gcj?

[Glenn Chambers <gchamber at bright dot net>]

On Tue, 2007-12-25 at 12:03 +0000, Andrew Haley wrote:
> Glenn Chambers writes:

>  > It's been a few years since I last played seriously in this area, but at
>  > that point, there were enough impedance mis-matches between C++ objects
>  > and Java objects that C-style glue layers turned out to be necessary.
>  > 
>  > In particular, code that threw or caught C++ exceptions couldn't also
>  > throw and catch Java exceptions.  This may have changed in recent
>  > versions; I'll let the developers clarify that point.
> 
> This works fine, and has for a long while.  I don't know how long ago
> you tried.

It was back in the early days of the 3.x series, as you can see from 
the FAQ entry I wrote on this subject.  (Check out entry 6.1)

If I can get some spare cycles, I'll have to update that example; the
problems with exception personalities are gone in the version 3.3 gcj
on my (quite old) SUSE install.

Replacement text for that example:

==> Makefile <==
sample:  sample.o sampNat.o
        gcj -o sample \
                sample.o sampNat.o -lstdc++ --main=sample

sample.o:  sample.class
        gcj -c sample.class

sample.class: sample.java
        gcj -C sample.java

sample.h: sample.class
        gcjh sample

sampNat.o: sample.h sampNat.cc
        g++ -c sampNat.cc

clean:
        rm -f sample sample.o sampNat.o sample.class sample.h

==> sample.java <==
public class sample {
  public native void myNative(String s);

  public void myJava(String s)
  {
    s = s + ", Java";
    System.out.println(s);
  }

  public static void main(String args[]) {
    sample x = new sample();
    x.myJava("Hello");
    x.myNative("Hello, Java (from C++)");
    x.myJava("Goodbye");
  }
}

==> sampNat.cc <==
#include <gcj/cni.h>
#include "sample.h"
#include <stream.h>
#include <java/io/PrintStream.h>
#include <java/lang/System.h>
#include <java/lang/String.h>

void sample::myNative(java::lang::String *s)
{
  // We can call the Standard Library
  cout << "Hello, C++" << endl;

  // We can also call Java library functions.
  java::lang::System::out->println(s);
}