Standard library header <cstdalign> (C++11)(until C++20), <stdalign.h> (C++11)

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

C compatibility header. alignas and alignof are keywords in C++, but they were not keywords in C until C23.


C compatibility macro constant, expands to integer literal 1
(macro constant)


<cstdalign> is deprecated in C++17 and removed in C++20. Corresponding <stdalign.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 __alignas_is_defined since C23
deprecated this
macro in C++

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