==== run ====
cc -O2 -pipe   -MD -MP  -c /home/src/regress/lib/libc/arc4random-fork/arc4random-fork.c
cc   -o arc4random-fork arc4random-fork.o 
./arc4random-fork

==== run-buf ====
./arc4random-fork -b

==== run-prefork ====
./arc4random-fork -p

==== run-buf-prefork ====
./arc4random-fork -bp