tcpdump -dd output doesn't match pcap_compile_nopcap

When I create a packet filter (eg for only tcp traffic) with

tcpdump -dd tcp

the packet filter output is

{ 0x28, 0, 0, 0x0000000c },
{ 0x15, 0, 2, 0x000086dd },
{ 0x30, 0, 0, 0x00000014 },
{ 0x15, 3, 4, 0x00000006 },
{ 0x15, 0, 3, 0x00000800 },
{ 0x30, 0, 0, 0x00000017 },
{ 0x15, 0, 1, 0x00000006 },
{ 0x6, 0, 0, 0x0000ffff },
{ 0x6, 0, 0, 0x00000000 },

But when I do the same programatically;

pcap_compile_nopcap(1500, DLT_EN10MB, &fcode, "tcp", 1, 0);
struct bpf_insn *insn = fcode.bf_insns;

for (i = 0; i < fcode.bf_len; ++insn, ++i)
{
  printf("{ 0x%x, %d, %d, 0x%08x },\n",
     insn->code, insn->jt, insn->jf, insn->k);
}

I get the following packet filter output:

{ 0x28, 0, 0, 0x0000000c },
{ 0x15, 0, 5, 0x000086dd },
{ 0x30, 0, 0, 0x00000014 },
{ 0x15, 6, 0, 0x00000006 },
{ 0x15, 0, 6, 0x0000002c },
{ 0x30, 0, 0, 0x00000036 },
{ 0x15, 3, 4, 0x00000006 },
{ 0x15, 0, 3, 0x00000800 },
{ 0x30, 0, 0, 0x00000017 },
{ 0x15, 0, 1, 0x00000006 },
{ 0x6, 0, 0, 0x000005dc },
{ 0x6, 0, 0, 0x00000000 },

Why are the two packet filters different?

Probably because the tcpdump on your system is built with an older version of libpcap than your program. The tcpdump on your system is probably using a libpcap without this change:

commit 58275c05a5cf9c3512bcbb1192ff351d32ccccbd
Author: Guy Harris <guy@alum.mit.edu>
Date:   Thu Sep 1 22:21:45 2011 -0700

    Handle some amount of IPv6 fragmentation.

    If we're checking for a particular protocol running on top of IPv6, and
    we're not doing full protocol-chain chasing for all "running on top of
    IPv6" tests, at least check for a fragmentation header before the header
    for the protocol.

and your program is probably using a libpcap with that change. That change went into libpcap somewhere in the libpcap 1.3.x timeframe.