Problem to call a Fortran subroutine in C++

[Americo Barbosa da Cunha Junior <junior dot americo at gmail dot com>]

I've trying to call a Fortran subroutine in a C++ code.

Below you can see the declaration of the subroutine and the part of C++ 
code that call it.


extern "C" {
extern void F_(int *n, double *tn, double *y, double *ftem, double 
*rpar, int *ipar);
}

// Jacobian
void jacobian(double **Jac, double *savf, double *y, double dt, int n)
{
   int i,j;
   double *ftem = malloc_vector(n);       // Vetor com Reaction Mapping 
Perturbado  
   double *rpar = malloc_vector(n);       // Vetor de trabalho double
   int    *ipar = malloc_ivector(n);          // Vetor de trabalho inteiro
   double *EWT = vector_ewt(y,n);      // Error Weight Vector
   double u = uround();                         // Roundoff
   double R, R0, FAC, tn;
 
   FAC = vector_wnorm(savf,EWT,n);
   R0 = 1000*fabs(dt)*u*FAC*(double)n;
   if( R0 == 0.0)
       R0 = 1.0;

   for(i = 0; i < n; i++)
   {
       R = max(sqrt(u)*fabs(y[i]),R0/EWT[i]);      // Perturbação
       y[i] += R;                                                    // 
Perturbando o vetor composicao
       F_(&n,&tn,y,ftem,rpar,ipar);                      // Preenche o 
ftem com o Reaction Mapping perturbado
       FAC = 1.0/R;
       for(j = 0; j < n; j++)
           Jac[i][j] = (ftem[j]-savf[j])*FAC;
   } 
}


Whem I try to link both languages the compiler returns the following 
error message: undefined reference to 'F_'

I did all procedures described in : 
http://www.physics.utah.edu/~detar/phycs6720/handouts/fortran_binding.html

Anybody can help me?

Thanks.

Americo Junior