< c‎ | types
Defined in header <stddef.h>
typedef /*implementation-defined*/ max_align_t;
(since C11)

max_align_t is a type whose alignment requirement is at least as strict (as large) as that of every scalar type.

[edit] Notes

Pointers returned by allocation functions such as malloc are suitably aligned for any object, which means they are aligned at least as strict as max_align_t.

max_align_t is usually synonymous with the largest scalar type, which is long double on most platforms, and its alignment requirement is either 8 or 16.

[edit] Example

#include <stdio.h>
#include <stddef.h>
#include <stdalign.h>
#include <stdlib.h>
#include <stdint.h>
#include <inttypes.h>
int main(void)
    size_t a = alignof(max_align_t);
    printf("Alignment of max_align_t is %zu (%#zx)\n", a, a);
    int *p = malloc(123);
    printf("The address obtained from malloc(123) is %#" PRIxPTR"\n",

Possible output:

Alignment of max_align_t is 16 (0x10)
The address obtained from malloc(123) is 0x1fa67010

[edit] See also

C++ documentation for max_align_t