std:: assume_aligned

Informs the implementation that the object ptr points to is aligned to at least N . 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 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 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 actually holds. A call to assume_aligned does not cause the compiler to verify or enforce this.

Example

See also