Re: [eclipse-clp-users] Probably a simple question to answer about using external C++ code for predicates

From: Kish Shen <kisshen_at_...5...>
Date: Fri, 18 May 2012 18:05:57 +0100
Hi Yvon,

_ZSt4cout is defined in g++'s standard C++ library (libstdc++), so it 
looks like you are not loading this library when you load 
cvode_interface.so. Did you link in libstdc++ when you compiled 
cvode_interface.so, and do you have LD_LIBRARY_PATH set correctly (i.e. 
libstdc++ is in one of the specified directories in LD_LIBRARY_PATH).
[I am assuming you are using Linux or Solaris, since your file has a .so 
extension]

I know you are showing a simplified version of your program, but in 
general, it does not make sense to have a main() procedure in code that 
is intended for a dynamic library (.so) [I think your error is also 
caused by  the use of the << output function]. In addition, sending 
output in your C++ code to stdout (as done in <<) is probably not a good 
idea, as this depends on where stdout is directed to in the ECLiPSe 
session you are loading your file into.

Cheers,

Kish

On 18/05/2012 03:23, Yvon Muc wrote:
> Greetings,
>
> I've simplified my problem down to the code at the end of my message.
> Basically it seems like as soon as I try to include any C++
> headers/libraries/code, the prolog file will no longer compile, complaining:
>
> cvode_interface.so: undefined symbol: _ZSt4cout
> problem while trying to load a shared library in load("cvode_interface.so")
> ERROR: heart.pl:9:
>     Query exited (abort): :- load(cvode_interface.so)
> External function does not exist in external_(t / 1, p_interfacetest,
> eclipse)
> ERROR: heart.pl:11:
>     Query exited (abort): :- external(t / 1, p_interfacetest)
>
> whereas if I comment out the 3 lines of C++ hello world, and uncomment
> the 2 lines of C hello world, prolog compiles without problem and my
> external predicate works as expected.  Both programs compile and run
> normally outside of prolog.
>
> I'm not sure what to make of this.  Help would be greatly appreciated.
> Do I need to make some changes to my makefile perhaps?
>
> Cheers,
>
> Yvon
>
>
> Prolog File
> ------------------------
>       :- load("cvode_interface.so").
>       :- external(t/1, p_interfacetest).
> ------------------------
>
>
> C++ file
> --------------------------------------------
> #include "eclipseclass.h"    /*Prolog Eclipse interfacing with C++ stuff*/
>
>
> #include<iostream>
> using namespace std;
> main(){cout<<  "Hello World in C++"<<  endl;}
>
> //#include<stdio.h>
> //main(){ printf("Hello World in C\n");}
>
> extern "C" int p_interfacetest() {
>       int test = 44;
>       return unify(EC_arg(1), EC_word(test));
> }
> --------------------------------------------
>
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Received on Fri May 18 2012 - 17:06:05 CEST

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