Re: isinf

[Dale Johannesen <dalej at apple dot com>]

On Jul 13, 2005, at 4:29 PM, Joe Buck wrote:
> On Thu, Jul 14, 2005 at 08:16:07AM +0900, Hiroshi Fujishima wrote:
> > Eric Botcazou <ebotcazou@libertysurf.fr> writes:
> >
> > > > The configure script which is included in rrdtool[1] checks whether
> > > > the system has isinf() as below.
> > > >
> > > > #include <math.h>
> > > > int
> > > > main ()
> > > > {
> > > > float f = 0.0; isinf(f)
> > > >   ;
> > > >   return 0;
> > > > }
> > >
> > > The test is clearly fragile.  Assigning the return value of isinf to 
> > > a
> > > variable should be sufficient for 4.0.x at -O0.
> >
> > Yes, I contact rrdtool maintainer.  Thank you.
>
> Best to make it a global variable, to guard against dead code 
> elimination.

Volatile would be even better.  It's valid to eliminate stores into 
globals
if you can determine the value isn't used thereafter, which we can here,
at least theoretically.