From: Alexandre Oliva <oliva@adacore.com>
To: Jonathan Wakely <jwakely.gcc@gmail.com>
Cc: gcc-patches <gcc-patches@gcc.gnu.org>,
"libstdc++" <libstdc++@gcc.gnu.org>,
Bernd Edlinger <bernd.edlinger@hotmail.de>
Subject: Re: [libstdc++] Use __gthread_join in jthread/95989
Date: Fri, 03 Mar 2023 05:18:33 -0300 [thread overview]
Message-ID: <or356ml02u.fsf@lxoliva.fsfla.org> (raw)
In-Reply-To: <CAH6eHdS94kvLApbEtzrDhCEyS7ca_8FGZ60HG5AV-E15cXe0Kg@mail.gmail.com>
On Feb 17, 2023, Jonathan Wakely <jwakely.gcc@gmail.com> wrote:
> The proper fix is to ensure the program has a non-weak reference to
> pthread_join without extra help (or use a recent glibc where it always
> works).
Indeed! How about this? Regstrapped on x86_64-linux-gnu, also tested
on arm-vx7r2 (gcc-12); verified that strong references are present in
95989.o, but not in libstdc++.a or .so. Ok to install?
(nit: the static local in a ctor of a template class may make for
multiple copies. Maybe a non-template always-inline function called by
all instantiations would be better.)
link pthread_join from std::thread ctor
Like pthread_create, pthread_join may fail to be statically linked in
absent strong uses, so add to user code strong references to both when
std::thread objects are created.
for libstdc++-v3/ChangeLog
* include/bits/std_thread.h (std::thread ctor): Add strong
reference to pthread_join.
---
libstdc++-v3/include/bits/std_thread.h | 1 +
1 file changed, 1 insertion(+)
diff --git a/libstdc++-v3/include/bits/std_thread.h b/libstdc++-v3/include/bits/std_thread.h
index adbd3928ff783..4bda350fa2c7b 100644
--- a/libstdc++-v3/include/bits/std_thread.h
+++ b/libstdc++-v3/include/bits/std_thread.h
@@ -145,6 +145,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
#ifdef GTHR_ACTIVE_PROXY
// Create a reference to pthread_create, not just the gthr weak symbol.
auto __depend = reinterpret_cast<void(*)()>(&pthread_create);
+ static auto __attribute__((__used__)) __depend_join = &pthread_join;
#else
auto __depend = nullptr;
#endif
--
Alexandre Oliva, happy hacker https://FSFLA.org/blogs/lxo/
Free Software Activist GNU Toolchain Engineer
Disinformation flourishes because many people care deeply about injustice
but very few check the facts. Ask me about <https://stallmansupport.org>
next prev parent reply other threads:[~2023-03-03 8:18 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-17 6:39 Alexandre Oliva
2023-02-17 10:58 ` Jonathan Wakely
2023-03-03 8:18 ` Alexandre Oliva [this message]
2023-03-03 9:33 ` Jonathan Wakely
2023-03-03 9:48 ` Jonathan Wakely
2023-03-03 17:46 ` Alexandre Oliva
2023-03-03 18:12 ` Jonathan Wakely
2023-03-03 18:14 ` Jonathan Wakely
2023-03-03 19:55 ` Alexandre Oliva
2023-03-03 20:15 ` Florian Weimer
2023-03-03 20:36 ` Alexandre Oliva
2023-03-03 20:57 ` Alexandre Oliva
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