Re: [avr-gcc-list] What Happened to the sbi() and cbi() Macros????

[Arthur Goldhammer]

I have to marvel at how long this rather futile debate has raged on. The 
issue involves two one-line macros, after all. Those who wish to pursue C 
expertise beyond the (hardly arcane) &=~ and |= constructs might want to 
consider how the job is done outside the world of AVRs. I also work with the 
Renesas M16C series of microcontrollers. Here's an excerpt from the standard 
header file provided with the free toolchain supplied by Renesas. Bit fields 
and unions are used to provide access to single bits in special function 
registers. To the objection that it's inefficient to set/clear 
non-contiguous bits by this method, the response, as Ned Konz noted in 
describing his rather similar code, is that byte access is also provided by 
the use of a union. I have no trouble adapting to this style when I program 
the M16C, and no trouble switching back to |= when programming the AVR.

Here's the Renesas code (excerpted to show just one of many SFRs and one set 
of mnemonic bit names):

#pragma ADDRESS  p0_addr  03e0H   /* Port P0 register */
....
/********************************************************
* declare SFR bit          *
********************************************************/
struct bit_def {
 char b0:1;
 char b1:1;
 char b2:1;
 char b3:1;
 char b4:1;
 char b5:1;
 char b6:1;
 char b7:1;
};

union byte_def{
struct bit_def bit;
char byte;
};
......
/*------------------------------------------------------
Port P0 register
------------------------------------------------------*/
union byte_def p0_addr;
#define  p0    p0_addr.byte

#define  p0_0   p0_addr.bit.b0  /* Port P0_0 register */
#define  p0_1   p0_addr.bit.b1  /* Port P0_1 register */
#define  p0_2   p0_addr.bit.b2  /* Port P0_2 register */
#define  p0_3   p0_addr.bit.b3  /* Port P0_3 register */
#define  p0_4   p0_addr.bit.b4  /* Port P0_4 register */
#define  p0_5   p0_addr.bit.b5  /* Port P0_5 register */
#define  p0_6   p0_addr.bit.b6  /* Port P0_6 register */
#define  p0_7   p0_addr.bit.b7  /* Port P0_7 register */

/*------------------------------------------------------

So, if you want to set bit 7 of port 0, it's
   p0_7 = 1;

Makes for easy reading. Whether the compiler can generate efficient code for 
this depends on the compiler, I suppose.
Art