Thank you.
I would have spent some time figuring this out and might not have done it in the end.
Gabi Voiculescu
--- On Thu, 7/9/09, Ian Lance Taylor <iant@xxxxxxxxxx> wrote:
> From: Ian Lance Taylor <iant@xxxxxxxxxx>
> Subject: Re: help understanding a gcc compilation issue
> To: "Gabi Voiculescu" <boy3dfx2@xxxxxxxxx>
> Cc: gcc-help@xxxxxxxxxxx
> Date: Thursday, July 9, 2009, 7:42 AM
> Gabi Voiculescu <boy3dfx2@xxxxxxxxx>
> writes:
>
> > When running, the function llrint() using and
> returning 64 bit variables fails to call rint(), and instead
> calls itself!?!.
> >
> > #include <stdio.h>
> > extern double rint(double x);
> >
> > long long llrint(double x);
> > long long llrint(double x)
> > {
> > printf("%s,%d llrint entry\n", __func__, __LINE__);
> //-gabi 07/08/2009
> > return (long long) rint(x);
> > }
> >
> > When calling llrint I see the print statement repeated
> forever, without calling rint() or returning from llrint().
>
> gcc is outsmarting itself. When it sees "(long long)
> rint(x)", it
> converts that into "llrint(x)". This is normally a
> safe conversion, but
> of course it is unsafe when you are trying to implement
> llrint itself.
> You can avoid this problem by using the -fno-builtin-rint
> option.
>
> Ian
>
