IGNORE_FRAMES    4034 gc/os_dep.c      npcs = backtrace((void **)tmp_info, NFRAMES + IGNORE_FRAMES);
IGNORE_FRAMES    4035 gc/os_dep.c      BCOPY(tmp_info+IGNORE_FRAMES, info, (npcs - IGNORE_FRAMES) * sizeof(void *));
IGNORE_FRAMES    4036 gc/os_dep.c      for (i = npcs - IGNORE_FRAMES; i < NFRAMES; ++i) info[i].ci_pc = 0;