arc4random in a nutshell


No setup required

Callable in 99% of software contexts
KERNEL
- anywhere except interrupt handlers
- from start of main(), maybe even during bootstrap

USERLAND
- even inside chroot (filesystem agnostic)
- pthreads (self locking)
- libraries may safely call it (no setup required)
- in signal handlers
- even when resource starved

Always succeeds -- and returns a random result