(guest, DragonFly cc 8.3 [DragonFly] Release/2019-02-22)
# cc -O2 -o write2633 write2633.c
# cc -O2 -o phase2 phase2.c
# cc -O2 -o verify2633 verify2633.c
(verify2633.c needed sys/stat.h added for fstat(2); otherwise no
 diagnostics, all binaries linked; same kernel build as DF-2632)