Re: What is wrong with Bugzilla? [Was: Re: GCC and Floating-Point]

[Robert Dewar <dewar at adacore dot com>]

Haren Visavadia wrote:

> test.c:
> #include <assert.h>
> #include <stdio.h>
>
> volatile float x = 3;
>
> int main()
> {
> 	float a = 1 / x;
> 	x = a;
> 	assert(a == x);
> 	printf("a has value of %g \n",a);
> 	printf("x has value of %g  \n",x);
> 	assert((int)a == 0);
> 	assert((int)x == 0);
> 	return 0;
> }
>
>
> Compile this gcc {-O0,-O1,-O2,-O3,-Os}
>
> You will notice it will always works  (despite not
> using  -ffloat-store) and not cause an assertion
> failure at all.

And so? Why would you expect this particular example
to give an assertion error. I would not expect an
assert error here. In unoptimized mode, you certainly
do not expect it, and in optimized mode, I would
expect the register tracker to know that a and x are
in the same register at the point of assertion (and
perhaps even eliminate the comparison entirely).