noexceptsafe

noexceptsafe is a C++ keyword introduced in C++20 that provides a mechanism to mark functions whose execution will not throw exceptions. It is a more powerful and expressive alternative to the noexcept specifier. Unlike noexcept, which can lead to undefined behavior if a function marked noexcept throws an exception, noexceptsafe guarantees that if a function marked noexceptsafe throws, the program will be terminated in a controlled manner via std::terminate. This allows for safer exception handling in situations where exception propagation is not desired or expected.

The primary benefit of noexceptsafe is enhanced safety and predictability. When a function is declared noexceptsafe, the compiler can perform further optimizations, knowing that no exceptions will propagate out of the function. This can lead to improved performance. Furthermore, if an exception is thrown from a noexceptsafe function, it indicates a programming error rather than an expected control flow. The immediate termination through std::terminate helps to pinpoint the source of the error more effectively during development and debugging.

noexceptsafe can be applied to functions, lambdas, and member functions. It is particularly useful for functions that are part of an interface where exception guarantees are critical, or for low-level operations where exception handling would add unnecessary overhead. The decision to use noexceptsafe should be made carefully, considering the implications of guaranteed termination upon an unexpected exception. It encourages a more robust design by enforcing a strict contract about exception behavior.