Re: New filesystem for Linux

[Mikulas Patocka <mikulas@artax.karlin.mff.cuni.cz>]

On Fri, 3 Nov 2006, Oleg Verych wrote:

> On Fri, Nov 03, 2006 at 06:09:39PM +0100, Mikulas Patocka wrote:
> > > In gmane.linux.kernel, you wrote:
> > > []
> > > > From: Andrew Morton <akpm@osdl.org>
> > > >
> > > > As Mikulas points out, (1 << anything) won't be evaluating to zero.
> > >
> > > How about integer overflow ?
> >
> > C standard defines that shifts by more bits than size of a type are
> > undefined (in fact 1<<32 produces 1 on i386, because processor uses only 5
> > bits of a count).
> ,--
> |#include <stdio.h>
> |int main(void) {
> |	unsigned int b = 1;
> |
> |	printf("%u\n", (1 << 33));
> |	printf("%u\n", (b << 33));
> |	return 0;
> |}
> |$ gcc bit.c && ./a.out
> `--
>
> There *is* difference, isn't it?

The standard says that the result is undefined, so the compiler is 
standard-compliant. It could have returned any numbers and still be 
correct.

Mikulas
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