[Swig-devel] [SWIG and Java]cast of lvalue used by SWIG

[Benjamin R. <ru...@ar...>]

Hi everybody!
I asked a question on SWIG-user mailing list and I think it is more
appropriate to ask it on this mailing list. This is a copy of the
message:

Hi everybody!
I have a problem of wrapping when I want use my wrapping generated by
SWIG from C++ to Java.
First I use a program in c++ to check if the code is good:

//file.cpp
#include <stdio.h>
#include "GModel.h" 
#include "GModelFactory.h"
#include "GVertex.h"

int main(int argc, char** argv)
{
        double x=1.0;
        double y=0.0;
        double z=0.0;
        double lc=0.1;  

        GModel *m = new GModel();
        GeoFactory *gFact=new GeoFactory();
        GVertex *v=gFact->addVertex(m, x, y, z, lc);
}

I check this code works.
Then I wrap with SWIG the code of c++ to java.
The execution of wrapping works and there is no error.
After I write an equivalent code in Java to do the same thing, and a
problem appears:

//Try.java
public class Try{
        static {
                try {
                        System.loadLibrary("Wrap");
                } catch (UnsatisfiedLinkError e) {
                        System.err.println("Native code library failed
to load. See the
chapter on Dynamic Linking Problems in the SWIG Java documentation for
help.\n" + e);
                        System.exit(1);
                }

        }
                
        public static void main(final String[] args) {
        
        double x=1.0;
        double y=0.0;
        double z=0.0;
        double lc=0.1;  

        GModel m = new GModel();
        GeoFactory gFact=new GeoFactory();
        GVertex v1=gFact.addVertex(m, x, y, z, lc);//the problem appears
here
        }
}

This java code does not work. The error is:

#
# A fatal error has been detected by the Java Runtime Environment:
#
#  SIGSEGV (0xb) at pc=0x00007f8814922724, pid=2064, tid=140222536300288
#
# JRE version: 6.0_24-b07
# Java VM: Java HotSpot(TM) 64-Bit Server VM (19.1-b02 mixed mode
linux-amd64 compressed oops)
# Problematic frame:
# C  [libWrap.so+0x1e724]  Java_WrapJNI_GeoFactory_1addVertex+0x4
#
# An error report file with more information is saved as:
# /home/benjamin/wrap_v1.2/wrap_v1.2/hs_err_pid2064.log
#
# If you would like to submit a bug report, please visit:
#   http://java.sun.com/webapps/bugreport/crash.jsp
# The crash happened outside the Java Virtual Machine in native code.
# See problematic frame for where to report the bug.
#
Abandon

To finish, I search the problem. I discover in cxx file generated by
SWIG an interesting behavior. Indeed, we have:

SWIGEXPORT jlong JNICALL Java_WrapJNI_new_1GeoFactory(JNIEnv *jenv,
jclass jcls) {
  jlong jresult = 0 ;
  GeoFactory *result = 0 ;
  
  (void)jenv;
  (void)jcls;
  result = (GeoFactory *)new GeoFactory();
  *(GeoFactory **)&jresult = result; 
  return jresult;
}

The cast at the left of equal sign is deprecated and not recommended
since gcc 3.5. If I modify this auto-generated file with:

SWIGEXPORT jlong JNICALL Java_WrapJNI_new_1GeoFactory(JNIEnv *jenv,
jclass jcls) {
  jlong jresult = 0 ;
  GeoFactory *result = 0 ;
  
  (void)jenv;
  (void)jcls;
  result = (GeoFactory *)new GeoFactory();
  jresult = (jlong)result;              //The only modification is here
  return jresult;
}

With this modification, the java program works.

Does somebody know this problem?
        
My OS is Ubuntu10.10
I use the SWIG 1.3.40, gcc 4.4

Thanks for your answers
        
Benjamin JEANTY-RUARD