NetBSD Problem Report #51139

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Message-Id: <20160515010955.C351D7AAAE@mollari.NetBSD.org>
Date: Sun, 15 May 2016 01:09:55 +0000 (UTC)
From: n54@gmx.com
Reply-To: n54@gmx.com
To: gnats-bugs@NetBSD.org
Subject: C++11 std::call_once() broken on NetBSD
X-Send-Pr-Version: www-1.0

>Number:         51139
>Category:       lib
>Synopsis:       C++11 std::call_once() broken on NetBSD
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    lib-bug-people
>State:          closed
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun May 15 01:10:00 +0000 2016
>Closed-Date:    Sat Aug 05 13:47:52 +0000 2017
>Last-Modified:  Sat Aug 05 13:47:52 +0000 2017
>Originator:     Kamil Rytarowski
>Release:        7.99.28 and 7.0
>Organization:
>Environment:
NetBSD chieftec 7.99.28 NetBSD 7.99.28 (GENERIC) #0: Wed Apr 27 05:36:02 CEST 2016  root@chieftec:/tmp/netbsd-tmp/sys/arch/amd64/compile/GENERIC amd64

And

NetBSD nb7_amd64 7.0 NetBSD 7.0 (GENERIC.201509250726Z) amd64
>Description:
The LLVM+Clang+LLDB buildbot has caught quickly a bug on NetBSD with std::call_once() in C++11.

http://reviews.llvm.org/D19271

It happened that std::call_once() as defined in C++11 doesn't work in 7.0 neither in HEAD (7.99.28).
>How-To-Repeat:
Build the following example and try to run.


#include <iostream>
#include <thread>
#include <mutex>

std::once_flag flag;

void simple_do_once()
{
    std::call_once(flag, [](){ std::cout << "Simple example: called once\n"; });
}

int main()
{
    std::thread st1(simple_do_once);
    st1.join();
}


<build>
g++ -std=c++11 -lpthread test.cpp
</build>

<run>

</run>
>Fix:
not investigated

>Release-Note:

>Audit-Trail:
From: Martin Husemann <martin@duskware.de>
To: gnats-bugs@NetBSD.org
Cc: lib-bug-people@netbsd.org, gnats-admin@netbsd.org,
	netbsd-bugs@netbsd.org
Subject: Re: lib/51139: C++11 std::call_once() broken on NetBSD
Date: Sun, 15 May 2016 09:31:43 +0200

 Program received signal SIGSEGV, Segmentation fault.
 [Switching to LWP 2]
 0x0000000000000000 in ?? ()
 (gdb) bt
 #0  0x0000000000000000 in ?? ()
 #1  0x00007f7ff780692e in pthread_once (
     once_control=once_control@entry=0x601d00 <flag>, 
     routine=0x400d50 <__once_proxy@plt>)
     at /usr/src/lib/libpthread/pthread_once.c:63
 #2  0x00000000004010cb in __gthread_once (__func=<optimized out>, 
     __once=0x601d00 <flag>) at /usr/include/g++/bits/gthr-default.h:699
 #3  std::call_once<simple_do_once()::<lambda()> > (__once=..., 
     __f=<optimized out>) at /usr/include/g++/mutex:729
 #4  simple_do_once () at test.cc:9
 #5  0x00007f7ff74a6dab in std::(anonymous namespace)::execute_native_thread_routine (__p=<optimized out>)
     at /usr/src/external/gpl3/gcc/dist/libstdc++-v3/src/c++11/thread.cc:84
 #6  0x00007f7ff780b1c1 in pthread__create_tramp (cookie=0x7f7ff7b19000)
     at /usr/src/lib/libpthread/pthread.c:576

 Name clash on weak symbols between libpthread and libstdc++ ?

 Martin

From: Valery Ushakov <uwe@stderr.spb.ru>
To: gnats-bugs@NetBSD.org
Cc: Martin Husemann <martin@duskware.de>
Subject: Re: lib/51139: C++11 std::call_once() broken on NetBSD
Date: Sun, 15 May 2016 13:54:53 +0300

 On Sun, May 15, 2016 at 07:35:00 +0000, Martin Husemann wrote:
 >  Name clash on weak symbols between libpthread and libstdc++ ?

 It works if -static, so more likely a bug ld.so vs. TLS.

 -uwe

From: Joerg Sonnenberger <joerg@bec.de>
To: gnats-bugs@NetBSD.org
Cc: lib-bug-people@netbsd.org, gnats-admin@netbsd.org,
	netbsd-bugs@netbsd.org, n54@gmx.com
Subject: Re: lib/51139: C++11 std::call_once() broken on NetBSD
Date: Sun, 15 May 2016 17:40:35 +0200

 On Sun, May 15, 2016 at 10:55:01AM +0000, Valery Ushakov wrote:
 > The following reply was made to PR lib/51139; it has been noted by GNATS.
 > 
 > From: Valery Ushakov <uwe@stderr.spb.ru>
 > To: gnats-bugs@NetBSD.org
 > Cc: Martin Husemann <martin@duskware.de>
 > Subject: Re: lib/51139: C++11 std::call_once() broken on NetBSD
 > Date: Sun, 15 May 2016 13:54:53 +0300
 > 
 >  On Sun, May 15, 2016 at 07:35:00 +0000, Martin Husemann wrote:
 >  >  Name clash on weak symbols between libpthread and libstdc++ ?
 >  
 >  It works if -static, so more likely a bug ld.so vs. TLS.

 That doesn't say much. With -static, the weak symbols are resolved
 differently, most noticable all weak versions are completely ignored in
 favor of the strong implementation.

 Joerg

From: Joerg Sonnenberger <joerg@bec.de>
To: gnats-bugs@NetBSD.org
Cc: lib-bug-people@netbsd.org, gnats-admin@netbsd.org,
	netbsd-bugs@netbsd.org
Subject: Re: lib/51139: C++11 std::call_once() broken on NetBSD
Date: Sun, 15 May 2016 18:03:17 +0200

 On Sun, May 15, 2016 at 01:10:00AM +0000, n54@gmx.com wrote:
 > It happened that std::call_once() as defined in C++11 doesn't work in
 > 7.0 neither in HEAD (7.99.28).

 Note that this issue is specific to libstdc++. libc++ works correctly.

 Joerg

From: Kamil Rytarowski <n54@gmx.com>
To: gnats-bugs@NetBSD.org
Cc: jwakely@redhat.com
Subject: Re: lib/51139: C++11 std::call_once() broken on NetBSD
Date: Wed, 21 Dec 2016 00:37:18 +0100

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 Subject: Re: lib/51139: C++11 std::call_once() broken on NetBSD
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 On 15.05.2016 18:05, Joerg Sonnenberger wrote:
 > The following reply was made to PR lib/51139; it has been noted by GNAT=
 S.
 >=20
 > From: Joerg Sonnenberger <joerg@bec.de>
 > To: gnats-bugs@NetBSD.org
 > Cc: lib-bug-people@netbsd.org, gnats-admin@netbsd.org,
 > 	netbsd-bugs@netbsd.org
 > Subject: Re: lib/51139: C++11 std::call_once() broken on NetBSD
 > Date: Sun, 15 May 2016 18:03:17 +0200
 >=20
 >  On Sun, May 15, 2016 at 01:10:00AM +0000, n54@gmx.com wrote:
 >  > It happened that std::call_once() as defined in C++11 doesn't work i=
 n
 >  > 7.0 neither in HEAD (7.99.28).
 > =20
 >  Note that this issue is specific to libstdc++. libc++ works correctly.=

 > =20
 >  Joerg
 > =20
 >=20

 libc++ doesn't use pthread_once(3)

 The problem is with TLS used in combination with libstdc++ for
 std::call_once.

 Everything works (for single threaded setup safe) if we remove __thread
 from the following fragment:

 namespace std _GLIBCXX_VISIBILITY(default)
 {
 _GLIBCXX_BEGIN_NAMESPACE_VERSION

 #ifdef _GLIBCXX_HAVE_TLS
   __thread void* __once_callable;
   __thread void (*__once_call)();
 #else
   // Explicit instantiation due to -fno-implicit-instantiation.
   template class function<void()>;
   function<void()> __once_functor;

   mutex&
   __get_once_mutex()
   {
     static mutex once_mutex;
     return once_mutex;
   }

   // code linked against ABI 3.4.12 and later uses this
   void
   __set_once_functor_lock_ptr(unique_lock<mutex>* __ptr)
   {
     __get_once_functor_lock_ptr() =3D __ptr;
   }

   // unsafe - retained for compatibility with ABI 3.4.11
   unique_lock<mutex>&
   __get_once_functor_lock()
   {
     static unique_lock<mutex> once_functor_lock(__get_once_mutex(),
 defer_lock);
     return once_functor_lock;
   }
 #endif

   extern "C"
   {
     void __once_proxy()
     {
 #ifndef _GLIBCXX_HAVE_TLS
       function<void()> __once_call =3D std::move(__once_functor);
       if (unique_lock<mutex>* __lock =3D __get_once_functor_lock_ptr())
       {
         // caller is using new ABI and provided lock ptr
         __get_once_functor_lock_ptr() =3D 0;
         __lock->unlock();
       }
       else
         __get_once_functor_lock().unlock();  // global lock
 #endif
       __once_call();
     }
   }

 _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace std

  --  src/external/gpl3/gcc/dist/libstdc++-v3/src/c++11/mutex.cc

 So far I have not reproduced this issue out of the libstdc++ context.
 Upstream reports that it might be related to ld.so and resolving
 __tls_get_addr, as it was causing trouble in the past.

 Perhaps something related:
 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D52192

 std::call_once is frequently used in LLDB.

 I've not reproduced this issue out of the libstdc++ context so far.


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From: "Kamil Rytarowski" <kamil@netbsd.org>
To: gnats-bugs@gnats.NetBSD.org
Cc: 
Subject: PR/51139 CVS commit: src/external/gpl3/gcc/dist/libstdc++-v3
Date: Wed, 21 Dec 2016 21:55:46 +0000

 Module Name:	src
 Committed By:	kamil
 Date:		Wed Dec 21 21:55:46 UTC 2016

 Modified Files:
 	src/external/gpl3/gcc/dist/libstdc++-v3/include/std: mutex
 	src/external/gpl3/gcc/dist/libstdc++-v3/src/c++11: mutex.cc

 Log Message:
 Add a walkaround for TLS bug in libstdc++ exposed with std::call_once

 Currently std::call_once with libstdc++ works only with static linking.
 Disable code path using __thread types and introduce FIXME_PR_51139.
 Problem discussed in PR 51139

 Functional std::call_once is required in LLVM and LLDB codebase.

 Example code to test std::call_once:
 #include <iostream>
 #include <thread>
 #include <mutex>
 #include <cstdlib>
 std::once_flag flag;
 int main(int argc, char **argv)
 {
         std::call_once(flag, [](){ std::cout << "Simple example: called once\n"; });
         return EXIT_SUCCESS;
 }

 Sponsored by <The NetBSD Foundation>


 To generate a diff of this commit:
 cvs rdiff -u -r1.1.1.4 -r1.2 \
     src/external/gpl3/gcc/dist/libstdc++-v3/include/std/mutex
 cvs rdiff -u -r1.1.1.2 -r1.2 \
     src/external/gpl3/gcc/dist/libstdc++-v3/src/c++11/mutex.cc

 Please note that diffs are not public domain; they are subject to the
 copyright notices on the relevant files.

From: "Kamil Rytarowski" <kamil@netbsd.org>
To: gnats-bugs@gnats.NetBSD.org
Cc: 
Subject: PR/51139 CVS commit: src/external/gpl3/gcc/dist/libstdc++-v3
Date: Sat, 24 Dec 2016 15:48:26 +0000

 Module Name:	src
 Committed By:	kamil
 Date:		Sat Dec 24 15:48:26 UTC 2016

 Modified Files:
 	src/external/gpl3/gcc/dist/libstdc++-v3/include/std: mutex
 	src/external/gpl3/gcc/dist/libstdc++-v3/src/c++11: mutex.cc

 Log Message:
 Revert introduction of FIXME_PR_51139

 This change introduced ABI incompatible change with older versions shipped
 on NetBSD. This back out code that is currently not working correctly due
 to TLS-based std::call_once implementation in GNU libstdc++.

 Error when starting gnuchash:

 /usr/pkg/lib/libwebkitgtk-1.0.so.0: Undefined symbol "_ZSt15__once_callable" (symnum = 1705)

 PR 51139

 Reported by <wiz>


 To generate a diff of this commit:
 cvs rdiff -u -r1.2 -r1.3 \
     src/external/gpl3/gcc/dist/libstdc++-v3/include/std/mutex
 cvs rdiff -u -r1.2 -r1.3 \
     src/external/gpl3/gcc/dist/libstdc++-v3/src/c++11/mutex.cc

 Please note that diffs are not public domain; they are subject to the
 copyright notices on the relevant files.

State-Changed-From-To: open->closed
State-Changed-By: kamil@NetBSD.org
State-Changed-When: Sat, 05 Aug 2017 15:47:52 +0200
State-Changed-Why:
Fixed by Joerg Sonnenberger
Fixed in NetBSD-current and pull-requested for NetBSD-8.
src/libexec/ld.elf_so: tls.c r. 1.11


>Unformatted:

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