On 2013-04-22 10:12:05 +0000, Warlich, Christof wrote:
> After all, this reminds be a bit of a hack lawver: A legal loophole
> shamelessly capitalizing upon ;-). At least, it violates the golden
> principle of "least surprise", being said to be an essential part of
> good software design.
> Anyhow, as I really need to deal with such situations: Is there a way
> to catch such conversion errors without cluttering the code with checks
> that test if still being within the range of a conversion or not? Skimming
> the paper linked by David suggests that it should be possible to
> install trap handlers for this purpose. Does anyone know how to do this
> with gcc?
I'm not sure, but indeed, there seems to be a bug, though your
program doesn't do the right test.
#include <stdio.h>
#include <fenv.h>
int main (void)
{
volatile float c = (volatile int) 0x7fffffbf;
printf ("inexact = %d\n", fetestexcept (FE_INEXACT));
c /= 123;
printf ("inexact = %d\n", fetestexcept (FE_INEXACT));
return 0;
}
outputs on Linux/x86_64 without optimization:
inexact = 0
inexact = 32
Is there any reason why the inexact flag isn't set for the
int-to-float conversion?
--
Vincent Lefèvre <vincent@xxxxxxxxxx> - Web: <http://www.vinc17.net/>
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Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)
