CFD Online Discussion Forums - how to compiled udf ?

hi all
i do have no idea about udf, udf1:

#include "udf.h"

static real v_prev = 0.0;

DEFINE_CG_MOTION(piston,dt,vel,omega,time,dtime)

{

Thread *t;

face_t f;

real NV_VEC(A);

real force, dv;

/* reset velocities */

NV_S(vel, =, 0.0);

NV_S(omega, =, 0.0);

if (!Data_Valid_P())

return;

/* get the thread pointer for which this motion is defined */

t = DT_THREAD(dt);

/* compute pressure force on body by looping through all faces */

force = 90.0;

begin_f_loop(f,t)

{

F_AREA(A,f,t);

force += F_P(f,t) * NV_MAG(A);

}

end_f_loop(f,t)

/* compute change in velocity, i.e., dv = F * dt / mass

velocity update using explicit Euler formula */

dv = dtime * force / 50.0;

v_prev += dv;

Message ("time = %f, x_vel = %f, force = %f\n", time, v_prev,

force);

/* set x-component of velocity */

vel[0] = v_prev;

}

it can be compiled like that:
http://b51.photo.store.qq.com/http_i...c6b9&a=57&b=51
http://b58.photo.store.qq.com/http_i...0cde&a=58&b=58

but udf 2:
#include "udf.h"
#include "unsteady.h"
#include "memory.h"
#include "stdlib.h"
#include "stdio.h"
DEFINE_CG_MOTION(movewall,dt,vel,omega,time,dtime)
{
Thread *t;
cell_t c;
real cx,cy;
//CArray<real,real&> vx,vy;
int i;
int n=0;
//if(!Data_Valid_P())
//return;
t=DT_THREAD(dt);
cx=0;
cy=0;
begin_c_loop(c,t)
{
//vx.Add(C_U(c,t));
//vy.Add(C_U(c,t));
cx=cx+C_U(c,t);
cy=cy+C_V(c,t);
n++;
}
end_c_loop(c,t);
cx=cx/n;
cy=cy/n;
cx=0;
cy=0.05;
vel[0]=cx;
vel[1]=cy;
//Message("\n n=%d, vx=%f, vy=%f\n",n,vel[0],vel[1]);
}
it can not be compiled :
http://b58.photo.store.qq.com/http_i...f0ca&a=58&b=58
http://b51.photo.store.qq.com/http_i...cc25&a=52&b=51

is anyone can help me?

thanks.