pp_hot.c
        if (CvDEPTH(cv) == 100 && ckWARN(WARN_RECURSION)
            && !(PERLDB_SUB && cv == GvCV(PL_DBsub)))
            sub_crush_depth(cv);

##</code><code>##

pp_ctl.c
                    if (CvDEPTH(cv) == 100 && ckWARN(WARN_RECURSION))
                        sub_crush_depth(cv);