[Bug libgcc/109540] New: Y2038: GCC gthr-posix.h weakref symbol invoking function has impact on time values

[Bug libgcc/109540] New: Y2038: GCC gthr-posix.h weakref symbol invoking function has impact on time values

[punitb20 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109540

            Bug ID: 109540
           Summary: Y2038: GCC gthr-posix.h weakref symbol invoking
                    function has impact on time values
           Product: gcc
           Version: 9.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libgcc
          Assignee: unassigned at gcc dot gnu.org
          Reporter: punitb20 at gmail dot com
  Target Milestone: ---

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.

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

[Bug libgcc/109540] Y2038: GCC gthr-posix.h weakref symbol invoking function has impact on time values

[punitb20 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109540

--- Comment #1 from Puneet B <punitb20 at gmail dot com> ---
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

[Bug libgcc/109540] Y2038: GCC gthr-posix.h weakref symbol invoking function has impact on time values

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109540

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
N.B. GCC 9 is no longer supported, so any changes will not help that version.

[Bug libgcc/109540] Y2038: GCC gthr-posix.h weakref symbol invoking function has impact on time values

[punitb20 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109540

--- Comment #3 from Puneet B <punitb20 at gmail dot com> ---
It can be reproduceable in gcc master branch or latest release..dont look at it
as GCC particular version bug.

[Bug libgcc/109540] Y2038: GCC gthr-posix.h weakref symbol invoking function has impact on time values

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109540

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Yes, I know. I'm just pointing out that you're reporting a bug against an
unsupported version.

[Bug libgcc/109540] Y2038: GCC gthr-posix.h weakref symbol invoking function has impact on time values

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109540

--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> ---
The description is a bit confusing, but the issue is that we define:

typedef struct timespec __gthread_time_t;

and then use that in several functions like this:

static inline int
__gthread_cond_timedwait (__gthread_cond_t *__cond, __gthread_mutex_t *__mutex,
                          const __gthread_time_t *__abs_timeout)
{
  return __gthrw_(pthread_cond_timedwait) (__cond, __mutex, __abs_timeout);
}


If libc uses a 64-bit time_t in struct timespec then we need to use
__pthread_cond_timedwait64 instead of pthread_cond_timedwait, because the
latter expects a struct containing a 32-bit time_t instead of a 64-bit one.

The weak alias referenced by __gthrw_ is defined like so:

static __typeof(pthread_cond_timedwait) __gthrw_pthread_cond_timedwait
__attribute__ ((__weakref__("pthread_cond_timedwait"), __copy__
(pthread_cond_timedwait)));

Where the _TIME_BITS=64 declaration of pthread_cond_timedwait is:

extern int pthread_cond_timedwait (pthread_cond_t *__restrict __cond,
pthread_mutex_t *__restrict __mutex, const struct timespec *__restrict
__abstime) __asm__ ("" "__pthread_cond_timedwait64")


The reported issue is that weakref("pthread_cond_timedwait") binds to a symbol
of that name, rather than to __pthread_cond_timedwait64, so we end up passing a
64-bit timespec to the 32-bit pthread_cond_timedwait.

However, that's not what I observe when I test it.

If I compile with 32-bit time_t for i686 using GCC 12 and
glibc-2.36-9.fc37.i686 then a call to __gthread_cond_timedwait will resolve to
glibc's pthread_cond_timedwait which expects a 32-bit timespec:


(gdb) 
13        __gthread_cond_timedwait(&cond, &mutex, &ts);
(gdb) step
__gthread_cond_timedwait (__cond=0x804c060 <cond>, __mutex=0x804c090 <mutex>,
__abs_timeout=0xffffc7e8)
    at /usr/include/c++/12/x86_64-redhat-linux/32/bits/gthr-default.h:872
872       return __gthrw_(pthread_cond_timedwait) (__cond, __mutex,
__abs_timeout);
(gdb) 
___pthread_cond_timedwait (cond=0x804c060 <cond>, mutex=0x804c090 <mutex>,
abstime=0xffffc7e8) at pthread_cond_wait.c:655
655     {
(gdb) l
650     libc_hidden_def (__pthread_cond_timedwait64)
651
652     int
653     ___pthread_cond_timedwait (pthread_cond_t *cond, pthread_mutex_t
*mutex,
654                                 const struct timespec *abstime)
655     {
656       struct __timespec64 ts64 = valid_timespec_to_timespec64 (*abstime);
657
658       return __pthread_cond_timedwait64 (cond, mutex, &ts64);
659     }


If I recompile the same code with -D_TIME_BITS=64 -D_FILE_OFFSET_BITS=64 then
the call to __gthread_cond_timedwait resolves to glibc's
__pthread_cond_timedwait64:

(gdb) 
13        __gthread_cond_timedwait(&cond, &mutex, &ts);
(gdb) step
__gthread_cond_timedwait (__cond=0x804c060 <cond>, __mutex=0x804c090 <mutex>,
__abs_timeout=0xffffc7e0)
    at /usr/include/c++/12/x86_64-redhat-linux/32/bits/gthr-default.h:872
872       return __gthrw_(pthread_cond_timedwait) (__cond, __mutex,
__abs_timeout);
(gdb) 
___pthread_cond_timedwait64 (cond=0x804c060 <cond>, mutex=0x804c090 <mutex>,
abstime=0xffffc7e0) at pthread_cond_wait.c:632
632     {
(gdb) l
627
628     /* See __pthread_cond_wait_common.  */
629     int
630     ___pthread_cond_timedwait64 (pthread_cond_t *cond, pthread_mutex_t
*mutex,
631                                  const struct __timespec64 *abstime)
632     {
633       /* Check parameter validity.  This should also tell the compiler that
634          it can assume that abstime is not NULL.  */
635       if (! valid_nanoseconds (abstime->tv_nsec))
636         return EINVAL;


So it seems to work fine. Do you actually observe a bug, or are you just
speculating from reading the wiki page and headers?

[Bug libgcc/109540] Y2038: GCC gthr-posix.h weakref symbol invoking function has impact on time values

[punitb20 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109540

--- Comment #6 from Puneet B <punitb20 at gmail dot com> ---
its not after refer the wiki, its observed on target where its clear that even
after compiling application with -D_TIME_BITS=64 -D_FILE_OFFSET_BITS=64 its
still calling ___pthread_cond_timedwait

More  over if i call pthread_cond_timedwait directly its calling
__pthread_cond_timedwait64 directly as i already mentioned in this thread.

And

issue is resolved  if i add  #defing GTHREAD_USE_WEAK 0   in
libgcc/gthr-posix.h 

it clears that weakref symbol is not working properly during linker stage.
both __gthrw_(pthread_cond_timedwait) and  pthread_cond_timedwait are expected
to invoke same API.

let me know if you need any more inputs

[Bug libgcc/109540] Y2038: GCC gthr-posix.h weakref symbol invoking function has impact on time values

[punitb20 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109540

--- Comment #7 from Puneet B <punitb20 at gmail dot com> ---
Any pointers here help to debug further.

[Bug libgcc/109540] Y2038: GCC gthr-posix.h weakref symbol invoking function has impact on time values

[punitb20 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109540

--- Comment #8 from Puneet B <punitb20 at gmail dot com> ---
could some one provide some pointers here? if its observed in gcc.9.3.0 and
fixed in latest GCC, please point me the same, i will pick and validate quickly

[Bug libgcc/109540] Y2038: GCC gthr-posix.h weakref symbol invoking function has impact on time values

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109540

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |WAITING
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2023-04-20

--- Comment #9 from Jonathan Wakely <redi at gcc dot gnu.org> ---
It works correctly with 10.4.1 and 11.3.0 and 12.1.0 so it looks like this
isn't true:

(In reply to Puneet B from comment #3)
> It can be reproduceable in gcc master branch or latest release..dont look at
> it as GCC particular version bug.

You haven't provided a testcase though, so we don't know what you're seeing.

[Bug libgcc/109540] Y2038: GCC gthr-posix.h weakref symbol invoking function has impact on time values

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109540

--- Comment #10 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Ah, it works for C++ because of r12-5108-g80fe172ba98201

With a recent glibc __gthread_cond_timedwait just calls pthread_cond_timedwait
directly, so use correctly redirected to __pthread_cond_timedwait64.

If you have glibc 2.34 then you can use -DGTHREAD_USE_WEAK=0 to disable the
weak refs in gthr-posix.h

[Bug libgcc/109540] Y2038: GCC gthr-posix.h weakref symbol invoking function has impact on time values

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109540

--- Comment #11 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Jonathan Wakely from comment #10)
> If you have glibc 2.34 then you can use -DGTHREAD_USE_WEAK=0 to disable the
> weak refs in gthr-posix.h

I think that is indeed the correct fix, as you originally asked about. But only
for glibc 2.34 and later.

[Bug libgcc/109540] Y2038: GCC gthr-posix.h weakref symbol invoking function has impact on time values

[punitb20 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109540

--- Comment #12 from Puneet B <punitb20 at gmail dot com> ---
Thanks for update , since we are using gcc-2.34 , this need to picked as fix.
but do you seen any side impact of this fix which need to be validated?

[Bug libgcc/109540] Y2038: GCC gthr-posix.h weakref symbol invoking function has impact on time values

[fw at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109540

Florian Weimer <fw at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           See Also|                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=103133
                 CC|                            |fw at gcc dot gnu.org

--- Comment #13 from Florian Weimer <fw at gcc dot gnu.org> ---
(In reply to Jonathan Wakely from comment #11)
> (In reply to Jonathan Wakely from comment #10)
> > If you have glibc 2.34 then you can use -DGTHREAD_USE_WEAK=0 to disable the
> > weak refs in gthr-posix.h
> 
> I think that is indeed the correct fix, as you originally asked about. But
> only for glibc 2.34 and later.

Only glibc 2.34 and later have this problem because previous upstream versions
lack dual-API time64 support. I would like to claim that we did this
deliberately, but the version alignment between libpthread removal and the new
time64 support was a bit of a coincidence.

[Bug libgcc/109540] Y2038: GCC gthr-posix.h weakref symbol invoking function has impact on time values

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109540

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |DUPLICATE
             Status|WAITING                     |RESOLVED

--- Comment #14 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Dup of bug 78017 for new enough glibc (which is all of ones that support
time64_t  IIRC).

*** This bug has been marked as a duplicate of bug 78017 ***