Re: [Discuss-gnuradio] Trial fix for F9 / OpenSuSE / gcc 4.3 make check failure (ticket:258)

[Philip Balister]

On Thu, Aug 14, 2008 at 9:20 PM, Eric Blossom <address@hidden> wrote:
> Revision 9296 contains a a trial fix for the make check
> problem we've been seeing with gcc 4.3 (F9 and OpenSuSE), ticket:258.
>
> The problem is that we were using a signed integer for a fixed point
> accumulator which we were counting on overflowing.
>
> According to the fine print in the C and C++ standards, if a signed
> integer type overflows, the result is undefined.  As of gcc 4.3, gcc
> was proving that our code was overflowing, and took advantage of the
> "undefined" result to short circuit the evaluation.
>
> Moral of the story: if you're using a fixed point phase accumulator,
> or anything else where you're counting on overflow happening, be sure
> that your variable is unsigned.
>
> See also http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37067 and
> http://www.airs.com/blog/archives/120
>
> Thanks to Stefan Bruens and Philip Ballister for working on this.

I just built GNU Radio trunk on Fedora 9 and make check ran until the
end. No obvious failures. This is an improvement over earlier
revisions.

Philip