How to remove "invalid type conversion: double -> pointer to char" Error??
 

I have written a UDF to define the Mass Source by the following equation

DEFINE_SOURCE(mass_source,c,t,dS,eqn)
{
real msource, b, bP, ba, kc ;
b = k0 * exp(AdsH/(R*C_T(c,t)))*op_pres;
bP = pow((k0/qm*exp(AdsH/(R*C_T(c,t)))*op_pres),tq);
ba = pow(bP,1/tq);
C_UDSI(c,t,0) = b / ba; /* C_eq ]g/g] equilibrium uptake*/

kc = 126.9889 * exp (-2757.8/C_T(c,t)); /*[s-1] corrected mass diffusion coeff by CFD simu*/

/* Computing instant uptake */
C_UDSI(c,t,1) = C_UDSI_M1(c,t,1) + kc * CURRENT_TIMESTEP * (C_UDSI(c,t,0) -C_UDSI_M1(c,t,1));

/* calculation dw/dt = ksav(Ceq - c_in);*/
C_UDSI(c,t,3) = (C_UDSI(c,t,1) - C_UDSI_M1(c,t,1)) / CURRENT_TIMESTEP ;/*dwbydt*/
/*C_UDSI(c,t,3) = ksav * (C_UDSI(c,t,0) - C_UDSI_M1(c,t,1));
/*mass source calculation*/
msource = -(1-bed_p) * dens_AC * C_UDSI(c,t,3); /*[kg/m3.s]*/

C_UDSI(c,t,4) = msource ;
/*dS[eqn] = - F0 * DbyRp2 * msource ;*/
/*C_UDSI(c,t,5) = - F0 * DbyRp2 * msource;*/
return msource;
}

When i interpret it, It shows the following Error in Line - 5.
"invalid type conversion: double -> pointer to char"

Please Suggest me something how to remove this Error????

Thanks.