Re: [avr-gcc-list] generic queue library for AVR GCC?

[Dave Hansen]

From: Andy Warner <address@hidden>

> Bruce D. Lightner wrote:
[...]
> >       #define begin_critical_section()  SREG, cli()
> >       #define end_critical_section(val) SREG = val
> >       ....
> >       {
> >           unsigned char sreg = begin_critical_section();
>
> Is that going to work the way you expect it to ?

I don't think so.

But

  unsigned char sreg;
  sreg = begin_critical_section();

should definitely work.

> I understood that the comma operator returns the type and
> value of the rightmost statement (which will be cli()
> in this example.)

But the comma operator has lower precedence than the assignment operator.   
So

  sreg = SREG, cli();

should parse as

  (sreg = SREG), (cli());

Which is why I question the original code, which mixes in a declaration.  
The = in the declaration is not an assignment operator, so I suspect that 
will parse as

  unsigned char sreg = (SREG, cli());

as you suggest.

Regards,
  -=Dave