Recently I saw this macro:
#define asOFFSET(s,m) ((size_t)(&reinterpret_cast<s*>(100000)->m)-100000)
I have found this as the approach to calculate the position offset of any item m of any struct s from the beginning of the structure.
However when I ran it and compared the calculation for two structures MyStuct2 and MyStruct3, which differ only by one int var3 added to MyStruct3 at the beginning, I got the difference 8 bytes, not 4 as I expected.
This is the code I run:
#include <time.h>
#include <stdio.h>
#define asOFFSET(s,m) ((size_t)(&reinterpret_cast<s*>(100000)->m)-100000)
struct MyStruct1 {int var1; int a;};
struct MyStruct2 {long var2; int a;};
struct MyStruct3 {int var3; long var4; int a;};
int main (void)
{
printf("%d\n",(int)asOFFSET(MyStruct1,a));
printf("%d\n",(int)asOFFSET(MyStruct2,a));
printf("%d\n",(int)asOFFSET(MyStruct3,a));
// Result:
// 4
// 8
// 16
}
and this is the output it gives:
4
8
16
My question is how can I fix the real memory in order to have one int taking 4 bytes and not 8?
Thanks.
