Anonymous union definition/declaration in a macro GNU vs VS2008

I am attempting to alter an IAR specific header file for a lpc2138 so it can compile with Visual Studio 2008 (to enable compatible unit testing).

My problem involves converting register definitions to be hardware independent (not at a memory address)

The "IAR-safe macro" is:

#define __IO_REG32_BIT(NAME, ADDRESS, ATTRIBUTE, BIT_STRUCT) \
                    volatile __no_init ATTRIBUTE union       \
                     {                                       \
                       unsigned long NAME;                   \
                       BIT_STRUCT NAME ## _bit;              \
                     } @ ADDRESS
//declaration
//(where __gpio0_bits is a structure that names 
//each of the 32 bits as P0_0, P0_1, etc)
__IO_REG32_BIT(IO0PIN,0xE0028000,__READ_WRITE,__gpio0_bits);
//usage
IO0PIN = 0x0xAA55AA55;
IO0PIN_bit.P0_5 = 0;

This is my comparable "hardware independent" code:

#define __IO_REG32_BIT(NAME, BIT_STRUCT)\
                    volatile union \
                     {                                 \
                       unsigned long NAME;             \
                       BIT_STRUCT NAME##_bit;      \
                     } NAME;
//declaration
__IO_REG32_BIT(IO0PIN,__gpio0_bits);
//usage
IO0PIN.IO0PIN = 0xAA55AA55;
IO0PIN.IO0PIN_bit.P0_5 = 1;

This compiles and works but quite obviously my "hardware independent" usage does not match the "IAR-safe" usage.

How do I alter my macro so I can use IO0PIN the same way I do in IAR? I feel this is a simple anonymous union matter but multiple attempts and variants have proven unsuccessful. Maybe the IAR GNU compiler supports anonymous unions and vs2008 does not.

Thank you.

Solution

Ok folks here's what ended up working for me:

#define __IO_REG32_BIT(NAME, BIT_STRUCT)\
    volatile union\
    {\
        unsigned long NAME;\
        BIT_STRUCT NAME##_bit;\
    } NAME##_type;

__IO_REG32_BIT(IO0PIN,__gpio0_bits);        

#define IO0PIN IO0PIN_type.IO0PIN
#define IO0PIN_bit IO0PIN_type.IO0PIN_bit

Now I can use the following in my code for unit testing:

IO0PIN = 0xFFFFFFFF;
IO0PIN_bit.P0_5 = 1;

And the preprocessor will replace it with:

IO0PIN_type.IO0PIN = 0xFFFFFFFF;
IO0PIN_type.IO0PIN_bit.P0_5 = 1;