state_saver - This class wrapper saves a copy of the current state of some object, and resets the object’s state at destruction time, undoing any change the object may have gone through.

attributes - Attributes for C++98 and later.

UNUSED - Macro with varying number of arguments to avoid "unused variable" warnings, with no effect on binary size, for C++11 and later.

concepts - Implementations concepts-like, for C++11 and later.

type_traits - Implementations of some type traits, for C++11 and later.

byte - Is a distinct type that implements the concept of byte as specified in the C++ language definition, with no aliasing to char, for C++17 and later.

utility - implementations of some utility functions, for C++17 and later.