harness_refclock.c: In function 'fpe_handler':
harness_refclock.c:41:60: warning: implicit declaration of function '_exit' [-Wimplicit-function-declaration]
 static void fpe_handler(int sig) { (void)sig; got_fpe = 1; _exit(42); }
                                                            ^~~~~
harness_refclock.c:41:60: warning: incompatible implicit declaration of built-in function '_exit'
harness_refclock.c: In function 'main':
harness_refclock.c:61:19: warning: unused variable 'ref_div' [-Wunused-variable]
  u32 nom = 25200, ref_div = 2, post_div = 1, fb_div_max = 0xFFFF;
                   ^~~~~~~