Re: [RFC 01/32] fs: introduce new 'struct inode_time'

Geert Uytterhoeven
2014-05-31T13:19:51Z

Hi Andreas,

On Sat, May 31, 2014 at 10:39 AM, Andreas Schwab <schwab@linux-m68k.org> wrote:
> Geert Uytterhoeven <geert@linux-m68k.org> writes:
>
>> Hi Arnd,
>>
>> On Fri, May 30, 2014 at 10:01 PM, Arnd Bergmann <arnd@arndb.de> wrote:
>>> + * The variant using bit fields is less efficient to access, but
>>> + * small and has a wider range as the 32-bit one, plus it keeps
>>> + * the signedness of the original timespec.
>>> + */
>>> +struct inode_time {
>>> + long long tv_sec : 34;
>>> + int tv_nsec : 30;
>>> +};
>>
>> Don't you need 31 bits for tv_nsec, to accommodate for the sign bit?
>> I know you won't really store negative numbers there, but storing a large
>> positive number will become negative on read out, won't it?
>
> Only if the int bitfield is signed. Bitfields are weird, aren't they? :-)

"int" is signed, right? Or do you mean a bitfield needs an explicit "signed"
keyword to be signed?

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds