[avr-chat] Is this efficient?

[Ruud Vlaming]

To find out if a register is in the io space in .c files,
i use the following, ugly, construct:

#undef  _SFR_IO8  
#define _SFR_IO8(arg) (arg) 
  #if (TIMSK < 0x40)
    blah blah  
  #else
    bloh bloh
  #endif
#undef  _SFR_IO8  
#define _SFR_IO8(arg) (*(volatile uint8_t *)((arg) + 0x20))

I cannot test it with _SFR_IO_REG_P, although that macro seems to be 
meant for the purpose:

  #if _SFR_IO_REG_P(TIMSK) 

for that gives the error:
  error: operator '*' has no left operand

Somewhere i am missing the point i guess. 
Who knows the proper way to do such things?

Ruud