[Help-gsl] Problem with GSL on my macbook

[Alexis Quentin]

Hi every one,
I want to use the GSL on my macbook. So I installed it using darwinports.
Then I wrote a C program :

#include <stdio.h>
#include <gsl/gsl_sf_bessel.h>

int
main (void)
{
  double x = 5.0;
  double y = gsl_sf_bessel_J0 (x);
  printf ("J0(%g) = %.18e\n", x, y);
  return 0;
}

I wrote it with XCode (Carbon). When I compile (with gcc), my terminal
answer me :
/usr/bin/ld: Undefined symbol:
_gsl_sf_bessel_J0
collect2: ld returned 1 exit status

Can you help me to make gsl working?