--- Daniel Berlin wrote:
>
> Let's take a duplicate of 323, 21809
>
>
> Compiling the code there with icc gives us:
>
> [EMAIL PROTECTED]:~> icc icca.c
> icca.c(7): warning #1572: floating-point equality
> and inequality
> comparisons are unreliable
> assert(a == x);
> ^
>
> ./[EMAIL PROTECTED]:~> ./a.out
> a.out: icca.c:7: main: Assertion `a == x' failed.
> Aborted
>
> In order to get icc to not generate an executable
> that will abort, you
> have to pass special flags (the same way we have
> -ffloat-store, except I
> believe their -mp flag will just disable any
> optimization that could get
> in the way of this working).
>
> One of these flag options is to tell it to use
> processor specific
> instructions, which auto turns on the equivalent of
> -mfpmath=sse.
>
Here is another case for you try out:
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.
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