Re: [Caml-list] Question about warning message.

[Shawn Wagner <shawnw@speakeasy.org>]

On Wed, May 05, 2004 at 06:47:15PM +0200, Xavier Leroy wrote:
> > my g++ compiler show me this warning:
> >     << warning: unused variable `int caml__dummy_n' >>
> > Here little lines of the function that generates this warning
> > ....
> > extern "C"
> > CAMLprim value
> > foo(value n) try {
> >   CAMLparam1(n);  (perhaps something lacks here?!?)
> >
> > I don't know where is the problem! Please, who can help me?
> 
> There's no problem with your code, and the warning is harmless.
> 
> It's just that the CAMLparam... macros used for GC root registration
> expand to complicated C code that happens to trigger the "unused
> variable" warning in gcc.  
> 
> David Brown suggest:
> 
> > BTW, what about having a
> >   (void) caml__dummy_##x;
> > at the end of the CAMLxparam... macros?  This does shut up the warning,
> > at least on gcc.
> 
> Thanks for the suggestion.  That might do the job.  I'll let the
> author of these macros (Damien Doligez) respond when he's back.
> 

A better solution for gcc (And, I think, icc) is to use the unused attribute
when the variable's declared.

Something like blah caml__dummy_##x __attribute__((__unused__));

-- 
Shawn Wagner
shawnw@speakeasy.org

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