problem with loader.sce (interfacing)

[Samy]

Hello, 
I'm trying to interface C programs with Scilab by using SWIG as it has been advised to me.
I have followed the process : 
* wrote the file "myfile.i"
* in the shell --> swig -scilab myfile.i (in the right directory)
* exec builder.sce in scilab
All seem to be working until here. Then I have to "exec loader.sce" in scilab but it doesn't work. 
I have an example for a very (very) simple function : 
* "essai.i" : 
[
%module essai

%{
int somme(int x, int y);
%}

extern int somme(int x, int y);
]

* "essai.c" :
[
#include 
int somme(int x, int y)
{
int res=x+y;
return res;
};
] 

* here is the error message after executing "loader.sce" : 
"
-->exec loader.sce

-->// This file is released into the public domain

-->// Generated by builder.sce : Please, do not edit this file

-->//

-->libessailib_path = get_file_path('loader.sce');

-->list_functions = [ 'somme';
-->];

-->addinter(libessailib_path+'/libessailib.so','libessailib',list_functions);
Link failed for dynamic library '/home/samy/Desktop/fonction1//libessailib.so'.
An error occurred: /home/samy/Desktop/fonction1//libessailib.so: undefined symbol: somme
Link failed for dynamic library '/home/samy/Desktop/fonction1//libessailib.so'.
An error occurred: /home/samy/Desktop/fonction1//libessailib.so: undefined symbol: somme
addinter(libessailib_path+'/libessailib.so','libessailib',list_functions);
!--error 236 
addinter: The shared archive was not loaded: (null)
at line 7 of exec file called by : 
exec loader.sce
"

I have tried to link the "libessailib.so" created after having executed "builder.sce". I link it just after executing "builder.sce" but I have a new error message : 
"
-->link('/home/samy/Desktop/fonction1/libessailib.so')
Link failed for dynamic library '/home/samy/Desktop/fonction1/libessailib.so'.
An error occurred: /home/samy/Desktop/fonction1/libessailib.so: undefined symbol: somme
!--error 236 
link: The shared archive was not loaded: (null)
"

I don't know why it does not work, I don't know if my file "essai.i" is not correct or if it is something else.

Could you help me please !!!

Thanks.

Samy