Hints to compiler that affects how code should be emitted or optimized. Hints may be compile time or runtime.
An identity function that hints to the compiler to be maximally pessimistic about what
black_box could do.
An identity function that causes an
unused_must_use warning to be
triggered if the given value is not used (returned, stored in a variable,
etc) by the caller.
Emits a machine instruction to signal the processor that it is running in a busy-wait spin-loop (“spin lock”).