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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. The program is ill-formed if N is not 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 object'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: __cpp_lib_assume_aligned 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) http://cppreference.com 2022.07.31 std::assume_aligned(3)
NAME | Synopsis | Return value | Exceptions | Notes | See also
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