PMTU discovery

Hello,
       I am checking ip_forward.c file and found there is no provision
for packet fragmentation. Is that corret?
       I think its because in current world all pcs start to use PMTU
discovery right? There is only checking condition that whether
forwarding packet requires fragmentation if yes then send ICMP frag
needed packet.
        Is there any probability that besided PMTU packet can be
fragmented or rejected?
regards,
cranium