# Module std::hint

1.27.0 · source ·
Expand description

Hints to compiler that affects how code should be emitted or optimized. Hints may be compile time or runtime.

## Functions

- must_use Experimental
  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.
- black_box
  An identity function that hints to the compiler to be maximally pessimistic about what `black_box` could do.
- spin_loop
  Emits a machine instruction to signal the processor that it is running in a busy-wait spin-loop (“spin lock”).
- unreachable_unchecked⚠
  Informs the compiler that the site which is calling this function is not reachable, possibly enabling further optimizations.