Guest compile (DragonFly 6.5-DEVELOPMENT, cc 8.3 [DragonFly] Release/2019-02-22):

$ cc -O2 -pthread -o /tmp/fd_timeout_uaf /tmp/fd_timeout_uaf.c
(no output, exit 0)

Baseline kernel: DragonFly 6.5-DEVELOPMENT #0: Thu Sep 17 20:25:05 UTC 2026
  root@dfbsd:/usr/obj/usr/src/sys/X86_64_GENERIC  x86_64
Patched  kernel: DragonFly 6.5-DEVELOPMENT #1: Thu Sep 17 20:51:04 UTC 2026
  root@dfbsd:/usr/obj/usr/src/sys/X86_64_GENERIC  x86_64
Kernel config delta (guest /usr/src/sys/config/X86_64_GENERIC):
  device		fdc0	at isa? port IO_FD1 irq 6 drq 2
  device		fd0	at fdc0 drive 0
  device		fd1	at fdc0 drive 1