From 21edd841611a97442a6b95e8ec7e91ff8fd3a451 Mon Sep 17 00:00:00 2001 From: Alexandre Oliva Date: Fri, 3 Mar 2023 15:59:36 -0300 Subject: [PATCH] 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 PR libstdc++/104852 PR libstdc++/95989 PR libstdc++/52590 * include/bits/std_thread.h (thread::_M_thread_deps): New static implicitly-inline member function. (std::thread template ctor): Pass it to _M_start_thread. * src/c++11/thread.cc (thread::_M_start_thread): Name depend parameter, force it live on entry. --- libstdc++-v3/include/bits/std_thread.h | 24 +++++++++++++++++------- libstdc++-v3/src/c++11/thread.cc | 10 ++++++++-- 2 files changed, 25 insertions(+), 9 deletions(-) diff --git a/libstdc++-v3/include/bits/std_thread.h b/libstdc++-v3/include/bits/std_thread.h index adbd3928ff78..e88c07fbd4f0 100644 --- a/libstdc++-v3/include/bits/std_thread.h +++ b/libstdc++-v3/include/bits/std_thread.h @@ -132,6 +132,22 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION thread() noexcept = default; #ifdef _GLIBCXX_HAS_GTHREADS + private: + // This adds to user code that creates std:thread objects (because + // it is called by the template ctor below) strong references to + // pthread_create and pthread_join, which ensures they are both + // linked in even during static linking. We can't depend on + // gthread calls to bring them in, because those may use weak + // references. + static void + _M_thread_deps_never_run() { +#ifdef GTHR_ACTIVE_PROXY + reinterpret_cast(&pthread_create)(); + reinterpret_cast(&pthread_join)(); +#endif + } + + public: template>> explicit @@ -142,18 +158,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION "std::thread arguments must be invocable after conversion to rvalues" ); -#ifdef GTHR_ACTIVE_PROXY - // Create a reference to pthread_create, not just the gthr weak symbol. - auto __depend = reinterpret_cast(&pthread_create); -#else - auto __depend = nullptr; -#endif using _Wrapper = _Call_wrapper<_Callable, _Args...>; // Create a call wrapper with DECAY_COPY(__f) as its target object // and DECAY_COPY(__args)... as its bound argument entities. _M_start_thread(_State_ptr(new _State_impl<_Wrapper>( std::forward<_Callable>(__f), std::forward<_Args>(__args)...)), - __depend); + _M_thread_deps_never_run); } #endif // _GLIBCXX_HAS_GTHREADS diff --git a/libstdc++-v3/src/c++11/thread.cc b/libstdc++-v3/src/c++11/thread.cc index 2d5ffaf678e9..c91f7b02e1f3 100644 --- a/libstdc++-v3/src/c++11/thread.cc +++ b/libstdc++-v3/src/c++11/thread.cc @@ -154,8 +154,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION } void - thread::_M_start_thread(_State_ptr state, void (*)()) + thread::_M_start_thread(_State_ptr state, void (*depend)()) { + // Make sure it's not optimized out, not even with LTO. + asm ("" : : "rm" (depend)); + if (!__gthread_active_p()) { #if __cpp_exceptions @@ -190,8 +193,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION } void - thread::_M_start_thread(__shared_base_type __b, void (*)()) + thread::_M_start_thread(__shared_base_type __b, void (*depend)()) { + // Make sure it's not optimized out, not even with LTO. + asm ("" : : "rm" (depend)); + auto ptr = __b.get(); // Create a reference cycle that will be broken in the new thread. ptr->_M_this_ptr = std::move(__b); -- 2.47.2