Defined in header <stddef.h> | ||
|---|---|---|
#define offsetof(type, member) /*implementation-defined*/ |
The macro offsetof expands to an integer constant expression of type size_t, the value of which is the offset, in bytes, from the beginning of an object of specified type to its specified member, including padding if any.
#include <stdio.h>
#include <stddef.h>
struct S {
char c;
double d;
};
int main(void)
{
printf("the first element is at offset %zu\n", offsetof(struct S, c));
printf("the double is at offset %zu\n", offsetof(struct S, d));
}Possible output:
the first element is at offset 0 the double is at offset 8
unsigned integer type returned by the sizeof operator (typedef) |
© cppreference.com
Licensed under the Creative Commons Attribution-ShareAlike Unported License v3.0.
http://en.cppreference.com/w/c/types/offsetof