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

Tue Dec 25 15:59:00 GMT 2007

On Tue, 2007年12月25日 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);
}