On Mon, Dec 1, 2025, at 11:35, Willy Tarreau wrote:
> On Mon, Dec 01, 2025 at 08:45:00AM +0100, Arnd Bergmann wrote:
>> On Sun, Nov 30, 2025, at 11:58, Willy Tarreau wrote:
>>
>> #if __TIMESIZE == 64 && __WORDSIZE == 32
>> # define __TIME_T_TYPE __SQUAD_TYPE
>> # define __SUSECONDS_T_TYPE __SQUAD_TYPE
>> #else
>> # define __TIME_T_TYPE __SLONGWORD_TYPE
>> # define __SUSECONDS_T_TYPE __SLONGWORD_TYPE
>> #endif
>>
>> so this one is explicitly the same width as tv_sec, which has all
>> the issues you listed, but avoids the need for padding.
>
> Ah we seem to just have checked different versions then,
> as in mine there was still some extra padding left depending
> on the endianness :-)
The padding is definitely there in timespec around tv_nsec,
just not in timeval.
Oddly, the version I quoted is from my arm64 /usr/include/
installation and looks different from what I see in the glibc
history, though that also uses a 64-bit tv_usec:
bits/typesizes.h:#define __SUSECONDS64_T_TYPE __SQUAD_TYPE
posix/bits/types.h:__STD_TYPE __SUSECONDS64_T_TYPE __suseconds64_t;
struct timeval
{
#ifdef __USE_TIME64_REDIRECTS
__time64_t tv_sec; /* Seconds. */
__suseconds64_t tv_usec; /* Microseconds. */
#else
__time_t tv_sec; /* Seconds. */
__suseconds_t tv_usec; /* Microseconds. */
#endif
};
>> C23 has updated the definition and does allow int64_t tv_nsec.
>
> So it purposely breaks existing apps or does it apply only to those
> compiled with -mstd=c23 ?
Neither, it's just that nolibc with a 64-bit tv_nsec would
be compliant with c23, just not earlier versions.
I expect glibc to stick with 32-bit timespec and padding, which
is still compliant with the new definition of
| The type of tv_nsec is an implementation-defined signed integer type
| that can represent integers in [0, 999999999].
>> I think it makes sense for nolibc to just follow the kernel's
>> definition here.
>
> Given the very narrow range of existing code that can be impacted,
> I'm fine, but in general I try to remain extremely cautious about
> portability: as a general rule, ifdefs needed to address possible
> incompatibilities, if any, should rather be in the libc code itself
> and not in the user application. I just ran a quick check and don't
> have code using &tv_usec nor &tv_nsec so here the risk remains quite
> low.
Ok
ARnd
