GCC warnings for unused global variables

[tm_gccmail@mail.kloo.net]

On Fri, 2 May 2003, Richard Henderson wrote:

> On Fri, May 02, 2003 at 08:38:44AM -0700, Kean Johnston wrote:
> > I don't know if such code exists, but it wouldn't surprise me terribly
> > if some smart bloke somewhere has organised, through link editor
> > trickery or other object-file manipulation, that code like:
> > 
> > static volatile int foo;
> > 
> > void doit (void)
> > {
> >   foo = 1;
> >   foo = 2;
> > }
> > 
> > actually orchestrates that because the symbol is marked as volatile,
> > whether static or not, that it is mapped to some I/O port or special
> > memory location or any number of possible things, and that the mere act
> > of assigning a value to it writes data to the port.
> 
> I suppose it's not impossible, however, that it's one of the
> least straightforward ways to accomplish this.  If I were going
> to have the link-editor place foo on some I/O port, then I'd
> declare it "extern", not "static".
> 
> > I belive that THAT
> > kind of trickery was the intent behind volatile.
> 
> We'll have to disagree then.  No one's come up with anything
> convincing so far.
> 
> 
> r~

We used a global volatile int for flags between the two SH2 processors on
a Sega 32x game system. So there are legitimate reasons.

Toshi