cppreference.net

Namespaces

Page

Variants

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

From cppreference.net

< cpp ‎ | header

Standard library headers

Language support
`<cfloat>`
`<climits>`
`<compare>` (C++20)
`<contracts>` (C++26)
`<coroutine>` (C++20)
`<csetjmp>`
`<csignal>`
`<cstdarg>`
`<cstddef>`
`<cstdint>` (C++11)
`<cstdlib>`
`<exception>`
`<initializer_list>` (C++11)
`<limits>`
`<new>`
`<source_location>` (C++20)
`<stdfloat>` (C++23)
`<typeinfo>`
`<version>` (C++20)
Concepts
`<concepts>` (C++20)
Diagnostics
`<cassert>`
`<cerrno>`
`<debugging>` (C++26)
`<stacktrace>` (C++23)
`<stdexcept>`
`<system_error>` (C++11)
Memory management
`<memory>`
`<memory_resource>` (C++17)
`<scoped_allocator>` (C++11)
Metaprogramming
`<type_traits>` (C++11)
`<ratio>` (C++11)

General utilities
`<any>` (C++17)
`<bitset>`
`<bit>` (C++20)
`<charconv>` (C++17)
`<expected>` (C++23)
`<format>` (C++20)
`<functional>`
`<optional>` (C++17)
`<stdbit.h>` (C++26)
`<tuple>` (C++11)
`<typeindex>` (C++11)
`<utility>`
`<variant>` (C++17)
Containers
`<array>` (C++11)
`<deque>`
`<flat_map>` (C++23)
`<flat_set>` (C++23)
`<forward_list>` (C++11)
`<hive>` (C++26)
`<inplace_vector>` (C++26)
`<list>`
`<map>`
`<mdspan>` (C++23)
`<queue>`
`<set>`
`<span>` (C++20)
`<stack>`
`<unordered_map>` (C++11)
`<unordered_set>` (C++11)
`<vector>`
Iterators
`<iterator>`
Ranges
`<generator>` (C++23)
`<ranges>` (C++20)

Algorithms
`<algorithm>`
`<numeric>`
Strings
`<cctype>`
`<cstring>`
`<cuchar>` (C++11)
`<cwchar>`
`<cwctype>`
`<string_view>` (C++17)
`<string>`
Text processing
`<clocale>`
`<codecvt>` ( C++11/17/26* )
`<locale>`
`<regex>` (C++11)
`<text_encoding>` (C++26)
Numerics
`<cfenv>` (C++11)
`<cmath>`
`<complex>`
`<linalg>` (C++26)
`<numbers>` (C++20)
`<random>` (C++11)
`<simd>` (C++26)
`<stdckdint.h>` (C++26)
`<valarray>`
Time
`<chrono>` (C++11)
`<ctime>`
C compatibility
`<ccomplex>` ( C++11/17/20* )
`<ciso646>` (until C++20)
`<cstdalign>` ( C++11/17/20* )
`<cstdbool>` ( C++11/17/20* )
`<ctgmath>` ( C++11/17/20* )

Input/output
`<cinttypes>` (C++11)
`<cstdio>`
`<filesystem>` (C++17)
`<fstream>`
`<iomanip>`
`<iosfwd>`
`<iostream>`
`<ios>`
`<istream>`
`<ostream>`
`<print>` (C++23)
`<spanstream>` (C++23)
`<sstream>`
`<streambuf>`
`<strstream>` ( C++98/26* )
`<syncstream>` (C++20)
Concurrency support
`<atomic>` (C++11)
`<barrier>` (C++20)
`<condition_variable>` (C++11)
`<future>` (C++11)
`<hazard_pointer>` (C++26)
`<latch>` (C++20)
`<mutex>` (C++11)
`<rcu>` (C++26)
`<semaphore>` (C++20)
`<shared_mutex>` (C++14)
`<stdatomic.h>` (C++23)
`<stop_token>` (C++20)
`<thread>` (C++11)
Execution support
`<execution>` (C++17)

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.

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

Notes

<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++