On Tuesday, April 21, 2015 06:42 PM, Ben Pope wrote:
89 SUMMARY: ThreadSanitizer: data race /home/ben/development/boost/test/build/boost_root/status/../boost/smart_ptr/detail/shared_count.hpp:449:49 in boost::detail::shared_count::shared_count(boost::detail::shared_count const&)
I've just been looking at this one, essentially it seems to boil down to: #include <atomic> #include <thread> #include <cstdint> typedef _Atomic( std::int_least32_t ) atomic_int_least32_t; inline void atomic_increment( atomic_int_least32_t * pw ) { __c11_atomic_fetch_add( pw, 1, __ATOMIC_RELAXED ); } int main() { atomic_int_least32_t use_count_; std::thread t ([&](){ atomic_increment(&use_count_); }); __c11_atomic_init( &use_count_, 1 ); t.join(); } clang -fsanitize=thread -std=c++14 -stdlib=libc++ -pthread -lc++ -lc++abi -g sp_counted_base.cpp -O0 ./a.out ================== WARNING: ThreadSanitizer: data race (pid=13176) Atomic write of size 4 at 0x7ffed833619c by thread T1: #0 __tsan_atomic32_fetch_add /home/ben/development/llvm/trunk/llvm/projects/compiler-rt/lib/tsan/rtl/tsan_interface_atomic.cc:614:3 (a.out+0x000000469c06) #1 atomic_increment(int _Atomic*) /home/ben/development/test/sp_counted_base.cpp:9:5 (a.out+0x0000004999c4) #2 main::$_0::operator()() const /home/ben/development/test/sp_counted_base.cpp:15:26 (a.out+0x00000049983e) #3 decltype(std::__1::forward<main::$_0>(fp)(std::__1::forward<>(fp0))) std::__1::__invoke<main::$_0>(main::$_0&&) /home/ben/development/llvm/trunk/install/release/bin/../include/c++/v1/__functional_base:415:12 (a.out+0x000000499563) #4 void std::__1::__thread_execute<main::$_0>(std::__1::tuple<main::$_0>&, std::__1::__tuple_indices<>) /home/ben/development/llvm/trunk/install/release/bin/../include/c++/v1/thread:337 (a.out+0x000000499563) #5 void* std::__1::__thread_proxy<std::__1::tuple<main::$_0>
(void*) /home/ben/development/llvm/trunk/install/release/bin/../include/c++/v1/thread:347 (a.out+0x000000499563)
Previous write of size 4 at 0x7ffed833619c by main thread: #0 main /home/ben/development/test/sp_counted_base.cpp:16:4 (a.out+0x000000498c39) Location is stack of main thread. Thread T1 (tid=13178, running) created by main thread at: #0 pthread_create /home/ben/development/llvm/trunk/llvm/projects/compiler-rt/lib/tsan/rtl/tsan_interceptors.cc:951:3 (a.out+0x000000422a21) #1 std::__1::thread::thread<main::$_0, void>(main::$_0&&) /home/ben/development/llvm/trunk/install/release/bin/../include/c++/v1/thread:359:16 (a.out+0x000000498f89) #2 main /home/ben/development/test/sp_counted_base.cpp:15:16 (a.out+0x000000498c30) SUMMARY: ThreadSanitizer: data race /home/ben/development/test/sp_counted_base.cpp:9:5 in atomic_increment(int _Atomic*) ================== ThreadSanitizer: reported 1 warnings I'm not sure how add_ref_copy is called during construction, but in the particular case I was looking at this seems to occur in the move constructor of thread: http://www.boost.org/development/tests/develop/developer/output/BenPope%20x8... Ben