exception at runtime, but get optimized into x = +inf.
see compiler optimizations above.
<p>
-Another x87 gcc bug is that comparision operators (==, <, etc)
+Another x87 gcc (<4.6) bug is that comparision operators (==, <, etc)
don't raise exceptions on nan
(eventhough this is required by ieee + c99 annex F).
(see <a href="http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52451">gcc bug52451</a>).