Standard library header <cstdbool> (C++11)(until C++20), <stdbool.h> (C++11)

This header was originally in the C standard library as <stdbool.h>.

Compatibility header. true, false and bool are keywords in C++, but they were not keywords in C until C23.

Macros
__bool_true_false_are_defined (C++11)(deprecated)	C compatibility macro constant, expands to integer literal 1 (macro constant)

Notes

<cstdbool> is deprecated in C++17 and removed in C++20. Corresponding <stdbool.h> is still available in C++20.

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
LWG 3827	C++11	C programs no longer need the compatibility macro __bool_true_false_are_defined since C23	deprecated this macro in C++