i686,SWIG+Perl, segmentation fault when using C structures

Hi,
when I tried to create a Perl module wich uses SWIG
wrappers for C
functions  several problems popped up:

1. After the  module is loaded the Perl script
produces segmentation
   fault. After I removed a simple statement like "my
$x=3.14;" it
   does not segfault anymore, but gives an error
"free(): invalid
   pointer". Also the output for the Perl script is
garbled.

2. If instead of working in linux-i686 machine I do
the same on
   sparc-solaris, the situation is just opposite:
without that
   statement Perl script produces "Bus Error", while
works almost fine
   with the statement included. On Solaris, though,
another strange
   hing happen - you have to quote variables like
   $Cstruct::cstruct->{key}, otherwise a null pointer
is passed to
   SWIG function. Printing the same variable using
Perl's print works
   fine.

The details are given below.

The Perl script SwigTest.pl loads Modules Cstruct.pm
and SwigTest.pm
(produced by SWIG). Cstruct.pm has a $cstruct variable
which is
initialized using cstruct_make(), a SWIG wrapper
around malloc().
The content of the $cstruct is printed using
print_string(), a SWIG
wrapper around printf().


Environment:
Linux: 
       uname -a:      i686, SuSE 9.1, kernel
2.6.5-7.108-default, 
       perl -v:       v5.8.3 built for
i586-linux-thread-multi,
       swig -version: SWIG Version 1.3.21, Compiled
with g++ [i686-pc-linux-gnu]

Solaris:
        uname -a:      SunOS 5.8 Generic_117000-01 sun4u
sparc,
        perl -v:       v5.8.5 built for sun4-solaris
        swig -version: SWIG Version 1.3.22, Compiled with g++
[sparc-sun-solaris2.8]

To run the example:

swig -perl -shadow SwigTest.i;
gcc -D_GNU_SOURCE -g -fPIC -mcpu=i686 -O3
-I/usr/include -I/usr/local/include
-I/usr/lib/perl5/5.8.3/i586-linux-thread-multi/CORE -c
SwigTest_wrap.c SwigTest.c;
ld -G SwigTest.o SwigTest_wrap.o -o SwigTest.so;
./Swigtest.pl;
        
You will have to adjust the path to perl executable
and  to perl CORE directory.

Here is the full source:

//--------------SwigTest.c--------------//
#include <stdio.h>
#include "SwigTest.h"

void print_string(const char * str)
{
    if(0==str)
        printf("ZERO POINTER!\n", str);
    else if(0==*str)
        printf("Empty string!\n", str);
    else
        printf("%s\n", str);
}

cstruct_t *cstruct_make()
{
    cstruct_t *cstruct;

    cstruct=(cstruct_t *)malloc(sizeof(cstruct_t));

    return(cstruct);
}
//--------------SwigTest.h--------------//
typedef struct cstruct {
    char *key;
} cstruct_t;

void print_string(const char * str);
cstruct_t * cstruct_make();
//--------------SwigTest.i--------------//
%module SwigTest

%{
#include <stdio.h>
#include "SwigTest.h"
%}

typedef struct cstruct {
    char *key;
} cstruct_t;


%name(print_string) extern void print_string(const
char *str);
%name(cstruct_make) extern cstruct_t *
cstruct_make(void);
//--------------Cstruct.pm--------------//
package Cstruct;

use strict;
use SwigTest;

use vars qw($hr $cstruct);

# This package provides access to two variables
# One is an ordinary perl hash, with one element
# The other is a hash tied via SWIG to a C structure
containing one element

my %hash;
$hr =\%hash;

# commenting (or uncommenting) the following statement
will cause
# crashes in Perl script that loads this module !!!
my $x=3.14;

$hr->{key} = "Contents of hash element with key
\"key\"";

$cstruct=SwigTest::cstruct_make() or die;
$cstruct->{key}="Contents of hash element linked via
Swig to C structure element";


print "[Loaded: ", __FILE__, "]\n";
1;
//-----------Swigtest.pl----------------//
#!/usr/gnu/bin/perl -w

use strict;
use lib (".");

use Cstruct;
use SwigTest;

print "\n\n";

print "\$Cstruct::hr is a                    
$Cstruct::hr\n";
print "\$Cstruct::cstruct is a               
$Cstruct::cstruct\n";

print "\n";

print "\$Cstruct::hr->{key} contains:       ";
print $Cstruct::hr->{key},"\n";
print "\$Cstruct::cstrcut->{key} contains:  ";
print $Cstruct::cstruct->{key},"\n";

print "\n";

print "When  \$Cstruct::hr->{key}       is passed to C
it contains: ";
SwigTest::print_string($Cstruct::hr->{key});

print "When  \$Cstruct::cstruct->{key}  is passed to C
it contains: ";
SwigTest::print_string($Cstruct::cstruct->{key});

print "When \"\$Cstruct::cstruct->{key}\" is passed to
C it contains: ";
SwigTest::print_string("$Cstruct::cstruct->{key}");

print "\n";
//--------------------------------------//


                
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