Re: Some cleanup patches for: '...lvalues is deprecated'

[Daniel Jacobowitz <dan@debian.org>]

On Sat, Jul 03, 2004 at 10:56:21PM +0200, Vojtech Pavlik wrote:
> On Sat, Jul 03, 2004 at 12:53:21PM +0000, Joel Soete wrote:
> > Hi Marcelo,
> > 
> > Please appolgies first for wrong presentation of previous post (that was 
> > the first and certainly the last time that I used the 'forwarding' option 
> > of this webmail interface :( ).
> > 
> > Here are some backport to clean up some warning of type: use of cast 
> > experssion
> > as lvalues is deprecated.
> > --- linux-2.4.27-rc2-pa4mm/kernel/sysctl.c.Orig	2004-06-29 
> > 09:03:42.000000000 +0200
> > +++ linux-2.4.27-rc2-pa4mm/kernel/sysctl.c	2004-06-29 
> > 10:10:31.588030256 +0200
> > @@ -890,7 +890,7 @@
> >  				if (!isspace(c))
> >  					break;
> >  				left--;
> > -				((char *) buffer)++;
> > +				buffer += sizeof(char);
> 
> This (although correct in the end) is a wrong thing to do.
> 
> It seems to look like the intention is to move the pointer by a char's
> size, however your change is equivalent to:
> 
> 	buffer += 1;
> 
> And if buffer wasn't void*, which it fortunately is, it would, unlike
> the older construction, move the pointer by a different size.
> 
> So just use
> 
> 	buffer++;
> 
> here, and the intent is then clear.

Except C does not actually allow incrementing a void pointer, since
void does not have a size.  You can't do arithmetic on one either.  GNU
C allows this as an extension.

It's actually this, IIRC:
  buffer = ((char *) buffer) + 1;

-- 
Daniel Jacobowitz