Hi,

Setting the ICMPPRINTFS option prevents the kernel from compiling. 
oip is a `struct ip *`. conf update included for convenience.

---
Index: arch/amd64/conf/GENERIC
===================================================================
RCS file: /cvs/src/sys/arch/amd64/conf/GENERIC,v
diff -u -p -u -p -r1.539 GENERIC
--- arch/amd64/conf/GENERIC     14 May 2026 16:20:27 -0000      1.539
+++ arch/amd64/conf/GENERIC     19 May 2026 02:30:24 -0000
@@ -22,6 +22,8 @@ option                NTFS            # NTFS support
 option         SUSPEND
 option         HIBERNATE

+option         ICMPPRINTFS
+
 config         bsd     swap generic

 mainbus0 at root
Index: netinet/ip_icmp.c
===================================================================
RCS file: /cvs/src/sys/netinet/ip_icmp.c,v
diff -u -p -u -p -r1.203 ip_icmp.c
--- netinet/ip_icmp.c   8 Jul 2025 00:47:41 -0000       1.203
+++ netinet/ip_icmp.c   19 May 2026 02:30:24 -0000
@@ -161,7 +161,7 @@ icmp_do_error(struct mbuf *n, int type,

 #ifdef ICMPPRINTFS
        if (icmpprintfs)
-               printf("icmp_error(%x, %d, %d)\n", oip, type, code);
+               printf("icmp_error(%p, %d, %d)\n", oip, type, code);
 #endif
        if (type != ICMP_REDIRECT)
                icmpstat_inc(icps_error);
---

Cheers,
Chris S.