RE: Y2038: GCC gthr-posix.h weakref symbol invoking function has impact on time values

["Puneet Kumar Yatnal (QUIC)" <quic_puneety@quicinc.com>]

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Here issue is weakref symbol in gcc not using the __asm_ function pointed by pthread.h instead its calling directly ___pthread_cond_timedwait which is exposed by version_symbol in pthread_cond_wait.c of glibc


From: Jonathan Wakely <jwakely.gcc@gmail.com>
Sent: Monday, April 17, 2023 12:53 PM
To: Andrew Pinski <pinskia@gmail.com>
Cc: Puneet Kumar Yatnal (QUIC) <quic_puneety@quicinc.com>; gcc-help <gcc-help@gcc.gnu.org>; gcc-bugs@gcc.gnu.org
Subject: Re: Y2038: GCC gthr-posix.h weakref symbol invoking function has impact on time values


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On Mon, 17 Apr 2023, 07:54 Andrew Pinski via Gcc-help, <gcc-help@gcc.gnu.org<mailto:gcc-help@gcc.gnu.org>> wrote:
On Sun, Apr 16, 2023 at 10:41 PM Puneet Kumar Yatnal (QUIC) via
Gcc-bugs <gcc-bugs@gcc.gnu.org<mailto:gcc-bugs@gcc.gnu.org>> wrote:
>
>
> ++
> From: Puneet Kumar Yatnal (QUIC)
> Sent: Monday, April 17, 2023 9:26 AM
> To: gcc-help@gcc.gnu.org<mailto:gcc-help@gcc.gnu.org>
> Subject: Y2038: GCC gthr-posix.h wekref symbol invoking function has impact on time values

First gcc-bugs@ is not the right place to report a bug report as
gcc-bugs is mainly for automated emails from bugzilla. Please use
bugzilla first.

>
> All
>
> if we fallowed https://sourceware.org/glibc/wiki/Y2038ProofnessDesign for Y2038 fix(where all timer related variable moved to 64 bit instead of 32 bit ), pthread_cond_timedwait function from gthr_posix.h is calling different function in pthrea_cond_wait.c of glibc(due to weakref of symbol pthread_cond_timedwait())  which impacting the time value.

Note libstdc++ does ABI changes too which is NOT part of that ABI design.
This is where the symbol
__gthread_cond_timedwait/__gthrw_pthread_cond_timedwait are used. So
any changes you might do to fix __gthrw_pthread_cond_timedwait is not
really going to work without wider ABI fixes to libstdc++.
I don't know any one who is making those changes/fixes. So you should
file an bug requesting it. And maybe even have a design document ready
for it. There are many/some classes which have timespec inside them

I don't think that's true. We don't use timespec members, they're just local variables, and very occasionally function parameters.



and not just the mutex related ones.

Thanks,
Andrew

>
> From pthread.h
> extern int pthread_cond_timedwait (pthread_cond_t *__restrict __cond, pthread_mutex_t *__restrict __mutex, const struct timespec *__restrict __abstime) __asm__ ("" "__pthread_cond_timedwait64")
>
> From gthread_posix.h:
> static __typeof(pthread_cond_timedwait) __gthrw_pthread_cond_timedwait __attribute__ ((__weakref__("pthread_cond_timedwait"), __copy__ (pthread_cond_timedwait)));
>
>
> __gthrw_(pthread_cond_timedwait) --> ___pthread_cond_timedwait   invoking in glibc instead of   __pthread_cond_timedwait64 which is impacting time value as __pthread_cond_timedwait is converting value from 32 bit to 64 bit.
>
> normal pthread_cond_timedwait is invoking __pthread_cond_timedwait64 properly and its working fine.
>
> From: pthread_cond_wait.c
>
> #if __TIMESIZE == 64
> strong_alias (___pthread_cond_timedwait64, ___pthread_cond_timedwait)
> #else
> strong_alias (___pthread_cond_timedwait64, __pthread_cond_timedwait64)
> libc_hidden_def (__pthread_cond_timedwait64)
>
> int
> ___pthread_cond_timedwait (pthread_cond_t *cond, pthread_mutex_t *mutex,
>                             const struct timespec *abstime)
> {
>   struct __timespec64 ts64 = valid_timespec_to_timespec64 (*abstime);
>
>   return __pthread_cond_timedwait64 (cond, mutex, &ts64);
> }
> #endif /* __TIMESIZE == 64 */
> versioned_symbol (libc, ___pthread_cond_timedwait,
>                   pthread_cond_timedwait, GLIBC_2_3_2);
> libc_hidden_ver (___pthread_cond_timedwait, __pthread_cond_timedwait)
> #ifndef SHARED
> strong_alias (___pthread_cond_timedwait, __pthread_cond_timedwait)
> #endif
>
> if add  #defing GTHREAD_USE_WEAK 0  in libgcc/gthr-posix.h issue is resolved but that is not correct way as it disable weakref for all symbol, please let me know what is correct way to fix this, this i observed with   gcc-9.3.0 gcc and glibc 2.34
>
> Regards
> Puneet
>