C++ Standard Attributes Studies

Attributes about warnings

deprecated - use when needed with string argument what to use instead
maybe_unused - use when needed and consider replacing your existent solutions
fallthrough - use when needed
nodiscard - use to signal wrong use of the API and add character literal argument

noreturn - to be used with std::rethrow_exception, std::nested_exception::rethrow_nested, std::throw_with_nested (always throw), std::abort, std::exit, std::quick_exit, std::terminate (always terminate the program), std::longjmp (always jump), std::unreachable (always undefined behavior). Exper only usage, introduces undefined behavior.
carries_dependency - never use
likely/unlikely - avoid, use only after improvement is measured, depends on compiler
assume - expert only usage, conditions should be an invariant to avoid undefined behavior, use only after improvement is measured

no_unique_address - use if binary size is critical, effects are not reliable or portable

deprecated - use when needed with string argument what to use instead
noreturn - to be used with std::rethrow_exception, std::nested_exception::rethrow_nested, std::throw_with_nested (always throw), std::abort, std::exit, std::quick_exit, std::terminate (always terminate the program), std::longjmp (always jump), std::unreachable (always undefined behavior). Exper only usage, introduces undefined behavior.
fallthrough - use when needed
nodiscard - use to signal wrong use of the API and add character literal argument
maybe_unused - use when needed and consider replacing your existent solutions
reproducible - equivalent to gnu::pure . Effectless (function has no observale side effects) and idempotent (repeated evaluation gives the same result). Assumed and optimised accordingly. If the assumption does not hold undefined behavior happens. Use only if you are sure what you are doing.
unsequenced - equivalent to gnu::const . Stateless (function does not define mutable static or thread local objects), effectless, idempotent and independent (does not depend on other state than the argument and constants). Assumed and optimised accordingly. If the assumption does not hold undefined behavior happens. Use only if you are sure what you are doing.