Messages in this thread | | | Date | Fri, 3 Nov 2006 19:14:59 +0100 (CET) | From | Mikulas Patocka <> | Subject | Re: New filesystem for Linux |
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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.
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