Index: amd64fbsd-nat.c
===================================================================
RCS file: /cvs/src/src/gdb/amd64fbsd-nat.c,v
retrieving revision 1.23
diff -u -p -r1.23 amd64fbsd-nat.c
--- amd64fbsd-nat.c	16 Oct 2009 23:18:27 -0000	1.23
+++ amd64fbsd-nat.c	19 Oct 2009 19:47:18 -0000
@@ -125,6 +125,11 @@ amd64fbsd_supply_pcb (struct regcache *r
   regcache_raw_supply (regcache, 14, &pcb->pcb_r14);
   regcache_raw_supply (regcache, 15, &pcb->pcb_r15);
 #if (__FreeBSD_version <  800075)
+  /* struct pcb provides the pcb_ds/pcb_es/pcb_fs/pcb_gs fields only
+     up until __FreeBSD_version 800074: The removal of these fields
+     occurred on 2009-04-01 while the __FreeBSD_version number was
+     bumped to 800075 on 2009-04-06.  So 800075 is the closest version
+     number where we should not try to access these fields.  */
   regcache_raw_supply (regcache, AMD64_DS_REGNUM, &pcb->pcb_ds);
   regcache_raw_supply (regcache, AMD64_ES_REGNUM, &pcb->pcb_es);
   regcache_raw_supply (regcache, AMD64_FS_REGNUM, &pcb->pcb_fs);