Standard library header <cstdbool> (C++11)(until C++20), <stdbool.h> (C++11)
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                    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) | 
[edit] Notes
<cstdbool> is deprecated in C++17 and removed in C++20. Corresponding <stdbool.h> is still available in C++20.
[edit] 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_definedsince C23 | deprecated this macro in C++ | 


