memalignment

Returns the maximum alignment satisfied by the provided address. The return value can be greater than any alignment value supported by the implementation. If p is a null pointer value, ​0​

If the return value compares is greater than or equal to alignof(T), the alignment requirement for the type T

A freestanding implementation needs to provide memalignment.

Parameters

Return value

The alignment value of p, or ​0​ if p is a null pointer value.

Notes

On common platforms where

• null pointers are cast to integer ​0​,
• pointer values are directly cast to the numeric values of virtual addresses, and
• size_t is same as uintptr_t,

this function can be implemented as return ( size_t )p & - ( size_t )p;

Example

#include <stdio.h>
#include <stdlib.h>
 
int main()
{
    alignas(128) int i = 0;
    printf("%zu\n%zu\n", memalignment(nullptr), memalignment(&i));
}

0
128

References

See also