Thread: How to pass locations of bit-field items?

Code:

{
    struct input_data
    {
    unsigned char gp1:1;
    unsigned char gp2:1;
    unsigned char gp3:1;
    unsigned char gp4:1;
    unsigned char gp5:1;
    unsigned char gp6:1;
    unsigned char gp7:1;
    unsigned char gp8:1;
    } in;

    struct eight_bit_words
    {
    unsigned char A:8;
    unsigned char B:8;
    } eight_bit;
} un;

I want to access the data in a variable such as un.eight_bit.A
from an external function, without passing the entire union. Apparently I can't get an address for an object in a union, so how do I do it?

Thanks in advance for your help.