Re: Does a zero-sized object in BSS go away?

[Thiemo Seufer <ica2_ts at csv dot ica dot uni-stuttgart dot de>]

Geoff Keating wrote:
[snip]
> > > ISO C programs can't create zero-size objects, but you can do it in
> > > GCC.
> > > 
> > > I think there's no way to tell if an object, which the program thinks
> > > is zero-size, actually has non-zero size.  So you could just make the
> > > common symbols have size 1 if the user asks for size 0...
> > 
> > This may break pointer comparisions. (Not that I knew of a good reason
> > to do this).
> 
> I don't see how this could break pointer comparisons.

Gcc allows to take the address of a zero-sized object:

struct a {
	int b[0];
	int c[0];
} d;

int main(void)
{
	return &d.b == &d.c;
}

> You can't meaningfully do them with zero-size objects anyway...

It's probably (hopefully :-) only a theoretical point and not a
practical issue.


Thiemo