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Re: What is wrong with Bugzilla? [Was: Re: GCC and Floating-Point]
On 2005-05-31 13:16:55 +0100, Andrew Haley wrote:
> Vincent Lefevre writes:
> > According to 5.1.2.3#13, 6.3.1.5#2 and 6.3.1.8#2, the assert should
> > not fail (unless the division yields a NaN, but that would be a very
> > bad implementation anyway).
>
> I have read the sections you mention, and I cannot see how they imply
> what you write. Can you explain, please?
Consider the example:
#include <assert,h>
volatile float x = 3;
int main()
{
float a = 1 / x;
x = a;
assert(a == x);
}
Concerning the line "float a = 1 / x;", 1 / x may be computed in
any extended precision, but when assigned to a, the result must
be converted to float (precision and range). Then concerning the
line "x = a;", since the type is the same, the value is unchanged.
And in the assert, a and x should have exactly the same value, so
that the comparison should return 1 (i.e., true).
--
Vincent Lefèvre <vincent@vinc17.org> - Web: <http://www.vinc17.org/>
100% accessible validated (X)HTML - Blog: <http://www.vinc17.org/blog/>
Work: CR INRIA - computer arithmetic / SPACES project at LORIA