Re: What's the purpose of these parentheses in the #define's?

[Philipp Janda <siffiejoe@...>]

Am 26.01.2015 um 08:51 schröbte William Ahern:
> On Sun, Jan 25, 2015 at 11:21:45PM -0600, Paige DePol wrote:
> > Niccolo Medici <niccolomedici@gmail.com> wrote:
> >
> > > Yes, I know about *that*. But the macros I'm talking about look like
> > > function calls. A comma (,) has the lowest precedence in C. So why do
> > > we need the parentheses? Let me modify your example:

We are not talking about the comma operator here but the 
argument/parameter delimiter for function-like macros, so the precedence 
of the former is irrelevant anyway.

> The macro arguments might themselves be comma expressions. So the
> parentheses aren't useless.

You can't have comma expressions without parentheses in argument lists.

    #define X(a, b) ...

    X(1, 2); /* ok */
    X(1, 2, 3); /* constraint violation: wrong number of arguments */
    X((1, 2), 3); /* ok, using comma expression as first argument */


Philipp