Negative integer passing from C to GNU-Prolog

Hello Prolog users,

I am trapped in passing negative integer value from C to Prolog using the
interface.

Here is the thing,
I have two files, one Prolog source code and a C source code.

Basically a variable defined in C has the value (*-2*), and the Prolog code
tries to read it in.

I use the standard interface like this in Prolog to get the value:

:- foreign(c_foo( -integer)).

However, even though the value defined in C code is *-2*, what I got in
Prolog (I write it out in Prolog after the above wrapper return) is
 4294967294


Follow the instruction
<http://www.gprolog.org/manual/html_node/gprolog068.html>,  I tried other
Foreign Type (positive, number ) which are like

:- foreign(c_foo( -positive)).

:- foreign(c_foo( -number)).

But it still gives me the wrong answer...

So I am wondering if it is possible to pass a negative integer from C to
GNU-Prolog..?

The attachments are the source code and Makefile, I have simplified it and
hope it could be understandable.

*The test is on Linux 14.04 64bit, GNU -Prolog 1.3.0*

Am I clear enough? Could anyone give me some help?

Best,
Shuai

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#include <gprolog.h>

int  babel_wrapper_foo(int  n)
      {
         int  return_value;

        int func;
        PlTerm arg[2];
        PlBool res;

        func = Pl_Find_Atom("foo"); 

        Pl_Query_Begin(PL_FALSE);

      arg[0] = Pl_Mk_Integer(n);

      arg[1] = Pl_Mk_Variable();

        res = Pl_Query_Call(func, 2, arg);

        return_value = Pl_Rd_Integer(arg[1]);

        Pl_Query_End(PL_KEEP_FOR_PROLOG);

        return return_value;
        }
      
int main(int argc , char **argv ) 
{ 
  Pl_Start_Prolog(argc, argv);
  babel_wrapper_foo(1);
  Pl_Stop_Prolog();
  return (0);
}

:- foreign(c_foo( -integer)).

foo(N, A_SSA_2) :- 
c_foo(TMP),
write(TMP), nl.

#include <gprolog.h>
#include <stdio.h>
#include <stdlib.h>

PlBool c_foo(int * ret) 
{
*ret = -2;
return PL_TRUE;
}