Naming portbits globally

I want to give a particular portbit a name, that I can use across multiple sourcefiles. To make portable code, I prefer to avoiding physical addresses. The only a approach I have been able to think of, is this:

foo.c:

#include <C8051F120.h>    // register definition file
#include <foo.h>

bdata unsigned char test;

sbit bit1 = test^3;
sbit bit2 = 0xB3;       // P3 has address 0xB0, ie. it is bitaddressable
sbit bit3 = P3^3;

foo.h:
extern bit bit1;
extern bit bit2;
extern bit bit2;


bar.c

#include <C8051F120.h>    // register definition file
#include <foo.h>

void myfunc(void)
{
    bit1 = 1;
    bit2 = 1;
    bit3 = 1;
}

It works fine for bit1 and bit2, but bit3 results in a linker warning “Reference made to unresolved external”. As sfr addresses, ending with 0 or 8 are byte- and bit addressable, I wonder why Keil complains about this, when the sbit in test can be handled.

Any alternative solutions?

Thanks, Glenn