Defined in header <stddef.h> | ||
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#define offsetof(type, member) /*implementation-defined*/ |
The macro offsetof expands to a constant 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) |
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C++ documentation for offsetof |
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