Re: [avr-gcc-list] Comma Operator in #define

[E. Weddington]

> Maybe I'm missing something, but I *did* check the ANSI C 
manual, and this
> should be OK, I think.
> 
> I want to use a comma operator in a macro (#define) 
statement:
> 
> #define set_clock(x) asm volatile("nop\n\t"::), (PORTB |= 
BIT3)
> 
> avr-gcc gives the following error when I use this macro:
> 
>   set_clock();
> 
> error: parse error before ',' token
> 
> If I just make it a ';', then everything works OK.
> 
> Any ideas?  What am I doing wrong?  Or is this a bug?
> 

AFAIK, the define body is composed of 2 seperate C 
statements which should be seperated by semicolon. A comma 
does not seperate C statements; a semicolon seperates C 
statements. (Sometimes in English too. ;-))

It's not a matter of whether a comma is allowed in macro, 
as so much whether the macro is defined to be legal C.