Re: [avr-libc-dev] Deprecation policy [was: Re: [RFC][PATCH] Deprecate inb / outb.]

[Russell Shaw]

Dmitry K. wrote:
> 16 Jun 2003 11:45 Russell Shaw wrote:
>
> > Dmitry K. wrote:
> >
> > > 16 Jun 2003 06:18 Joerg Wunsch wrote:
> > >
> > > > Basically, it's now no longer (easily) possible to use one
> > > > of the SFRs as the target of an inline asm statement anyway (see bug
> > > > ID #2233, we need to update our inline asm docs accordingly).
> > >
> > > Examples of SFRs usage:
> > >
> > > //#define _SFR_ASM_COMPAT  1    /* needed for second example only       */
> > >
> > > #include <avr/io.h>
> > >
> > > /* Examples of SFRs as the target of an inline asm statements.
> > >   For qualitative realization it is necessary to add check:
> > >         if (__builtin_constant_p((port)))
> > > */
> > > #define cbi_atomic(port,bit)    do {                    \
> > ...
> > > } while (0)
> >
> > What is the do{...} while(0) for?
>
>
> I shall specify, superfluous here only internal brackets. Removal
> "do ... while" is undesirable, as, for example, it will be impossible to 
> write:
>         if (flag)
>                 cbi_atomic(PORTB, 2);   /* excess ';'   */
>         else
> ==>  parse error before "else"

Hi,
The reason i asked is that why couldn't just the curly brackets
be used like:

  #define cbi_atomic(port,bit)    {                    \
  ...
  }