pub fn black_box<T>(dummy: T) -> T
An identity function that hints to the compiler to be maximally pessimistic about what
black_box could do.
std::convert::identity, a Rust compiler is encouraged to assume that
dummy in any possible valid way that Rust code is allowed to without introducing undefined
behavior in the calling code. This property makes
black_box useful for writing code in which
certain optimizations are not desired, such as benchmarks.
Note however, that
black_box is only (and can only be) provided on a “best-effort” basis. The
extent to which it can block optimisations may vary depending upon the platform and code-gen
backend used. Programs cannot rely on
black_box for correctness in any way.