Consteval
Consteval is a C++20 feature that designates a function as an immediate function, meaning it must be evaluated at compile-time and cannot be called at runtime. It ensures that the function's execution and result are computed during compilation, providing stronger guarantees than constexpr functions, which can also run at runtime. This enables more predictable performance and allows for compile-time validation of arguments or computations.
Developers should use consteval when they need to enforce compile-time evaluation for functions that must not incur runtime overhead, such as in metaprogramming, template computations, or when generating constant data like lookup tables. It is particularly useful in performance-critical applications where eliminating runtime costs is essential, and in scenarios requiring compile-time error checking, such as validating configuration parameters or mathematical constants.