Sorry I could not get about SIGSEGV. I interpreted and checked it by compiling separately but the result is same. How I can debug my UDF? I checked on internet they are saying different reasons. when when udf could not access variable. nPlease have a look in my udf.n#include mem.hnDEFINE_PROFILE(mfm_h, thread, position)n{n double mh, mc, fh, fc;n real x[ND_ND];n face_t f;n Thread *t0, *t1;n cell_t c0, c1;n begin_f_loop(f, thread)n {n c0 = F_C0(f, thread);n t0 = THREAD_T0(thread);n c1 = F_C1(f, thread);n t1 = THREAD_T1(thread);n  fh = C_YI(c0, t0, 0);n  fc = C_YI(c1, t1, 0);n  mh = fh*0.95;n  mc = fc+fh-mh;n F_PROFILE(f, thread, position)= mh;n }n end_f_loop(f, thread)n}Regards,nAbbas n