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Defined in header <memory> | ||
template<std::size_t N,class T> constexpr T* assume_aligned( T* ptr); | (since C++20) | |
Informs the implementation that the objectptr points to is aligned to at leastN. The implementation may use this information to generate more efficient code, but it might only make this assumption if the object is accessed via the return value ofassume_aligned.
N must be a power of 2. The behavior is undefined ifptr does not point to an object of typeT (ignoring cv-qualification at every level), or if the object's alignment is not at leastN.
Contents |
ptr.
Throws nothing.
To ensure that the program benefits from the optimizations enabled byassume_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 actually holds. A call toassume_aligned does not cause the compiler to verify or enforce this.
| Feature-test macro | Value | Std | Feature |
|---|---|---|---|
__cpp_lib_assume_aligned | 201811L | (C++20) | std::assume_aligned |
| This section is incomplete Reason: no example |
alignof(C++11) | queries alignment requirements of a type (operator)[edit] |
alignas(C++11) | specifies that the storage for the variable should be aligned by specific amount (specifier)[edit] |
(since C++11)(deprecated in C++23) | defines the type suitable for use as uninitialized storage for types of given size (class template)[edit] |
(C++11) | aligns a pointer in a buffer (function)[edit] |
[[assume(expression)]](C++23) | specifies that theexpression will always evaluate totrue at a given point (attribute specifier)[edit] |
