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std::assume_aligned(3) C++ Standard Libary std::assume_aligned(3) NAME std::assume_aligned - std::assume_aligned Synopsis Defined in header <memory> template< std::size_t N, class T > (since C++20) [[nodiscard]] constexpr T* assume_aligned( T* ptr ); Informs the implementation that the object ptr points to is aligned to at least N. The implementation may use this information to generate more effi- cient code, but it might only make this assumption if the object is accessed via the return value of assume_aligned. N must be a power of 2. The behavior is undefined if ptr does not point to an object of type T (ignoring cv-qualification at every level), or if the ob- ject's alignment is not at least N. Return value ptr. Exceptions Throws nothing. Notes To ensure that the program benefits from the optimizations enabled by assume_aligned, it is important to access the object via its return value: void f(int* p) { int* p1 = std::assume_aligned<256>(p); // Use p1, not p, to ensure benefit from the alignment assumption. // However, the program has undefined behavior if p is not aligned // regardless of whether p1 is used. } It is up to the program to ensure that the alignment assumption ac- tually holds. A call to assume_aligned does not cause the compiler to verify or en- force this. Feature-test macro Value Std Feature __cpp_lib_assume_aligned 201811L (C++20) std::assume_aligned Example This section is incomplete Reason: no example See also alignof operator(C++11) queries alignment requirements of a type alignas specifier(C++11) specifies that the storage for the variable should be aligned by specific amount aligned_storage defines the type suitable for use as uninitialized (C++11)(deprecated in C++23) storage for types of given size (class template) align aligns a pointer in a buffer (C++11) (function) specifies that the expression will al- ways evaluate to [[assume(expression)]](C++23) true at a given point (attribute specifier) Category: * Todo no example http://cppreference.com 2024.06.10 std::assume_aligned(3)
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