How to know the offset of a member in a struct from the beginning of a struct body

#include<Stdio.H>
#DefineStruct_offset(Stru_name,Element)(unsigned Long)&((structStru_name*)0)->Element
structStru_addr
{
intA;
CharB;
intD;
CharC;

};

intMain(void)
{
structSTRU_ADDR s;
printf("Start addr of s =%x\n",&S.A);

unsignedLongOffset=Struct_offset(Stru_addr,C);This is the relative address of the member C relative to the first address.


printf("c_addr =%x, offset =%u\n",&S.C,Offset);
printf("Start addr of S caculated from C addr:%x\n",(Char*)&S.C-Offset);//This is the first address.
return0;
}

( unsigned long ) & ( ( struct  stru_name* ) 0 " - > element.

The results of the above program execution are as follows:

Start addr of s = bfad7ac0
C_ADDR = BFAD7ACC, offset = 12
Start addr of S caculated from C addr:bfad7ac0


The above results also take into account the alignment problem in the structure body.

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How to know the offset of a member in a struct from the beginning of a struct body