Fix fbvector::assign(size, v) for no-reallocation case. #21
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Also add a test case.
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Thanks! We'll look into this. |
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... and good to see you again, Christian :) |
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Just pushed a near-rewrite of FBVector. Looks like the new assign() no longer has this bug; thanks for reporting it, though. |
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Summary: Exposed by UBSAN's unsigned-integer-overflow: ``` > folly/experimental/observer/detail/Core.cpp:179:9: runtime error: unsigned integer overflow: 0 - 1 cannot be represented in type 'size_t' (aka 'unsigned long') > #0 0x7f605837dfea in folly::observer_detail::Core::removeStaleDependents()::$_4::operator()(std::vector<std::weak_ptr<folly::observer_detail::Core>, std::allocator<std::weak_ptr<folly::observer_detail::Core> > >&) const folly/experimental/observer/detail/Core.cpp:179 > #1 0x7f6058344b0c in auto folly::SynchronizedBase<folly::Synchronized<std::vector<std::weak_ptr<folly::observer_detail::Core>, std::allocator<std::weak_ptr<folly::observer_detail::Core> > >, folly::SharedMutexImpl<false, void, std::atomic, false, false> >, (folly::detail::MutexLevel)1>::withWLock<folly::observer_detail::Core::removeStaleDependents()::$_4>(folly::observer_detail::Core::removeStaleDependents()::$_4&&) folly/Synchronized.h:210 > #2 0x7f6058344917 in folly::observer_detail::Core::removeStaleDependents() folly/experimental/observer/detail/Core.cpp:174 > #3 0x7f60583785cb in folly::observer_detail::Core::~Core()::$_2::operator()(std::unordered_set<std::shared_ptr<folly::observer_detail::Core>, std::hash<std::shared_ptr<folly::observer_detail::Core> >, std::equal_to<std::shared_ptr<folly::observer_detail::Core> >, std::allocator<std::shared_ptr<folly::observer_detail::Core> > > const&) const folly/experimental/observer/detail/Core.cpp:156 > #4 0x7f6058343cdc in auto folly::SynchronizedBase<folly::Synchronized<std::unordered_set<std::shared_ptr<folly::observer_detail::Core>, std::hash<std::shared_ptr<folly::observer_detail::Core> >, std::equal_to<std::shared_ptr<folly::observer_detail::Core> >, std::allocator<std::shared_ptr<folly::observer_detail::Core> > >, folly::SharedMutexImpl<false, void, std::atomic, false, false> >, (folly::detail::MutexLevel)1>::withWLock<folly::observer_detail::Core::~Core()::$_2>(folly::ob server_detail::Core::~Core()::$_2&&) folly/Synchronized.h:210 > #5 0x7f6058343a17 in folly::observer_detail::Core::~Core() folly/experimental/observer/detail/Core.cpp:154 > #6 0x7f605838b8ca in std::_Sp_counted_ptr<folly::observer_detail::Core*, (__gnu_cxx::_Lock_policy)2>::_M_dispose() buck-out/cells/fbsource/gen/third-party/gcc/7.x/stdc++-headers#header-mode-symlink-tree-with-header-map,headers/bits/shared_ptr_base.h:378 > #7 0x7f605834d411 in std::_Sp_counted_base<(__gnu_cxx::_Lock_policy)2>::_M_release() buck-out/cells/fbsource/gen/third-party/gcc/7.x/stdc++-headers#header-mode-symlink-tree-with-header-map,headers/bits/shared_ptr_base.h:156 > #8 0x7f605834d332 in std::__shared_count<(__gnu_cxx::_Lock_policy)2>::~__shared_count() buck-out/cells/fbsource/gen/third-party/gcc/7.x/stdc++-headers#header-mode-symlink-tree-with-header-map,headers/bits/shared_ptr_base.h:686 > #9 0x7f605834d23a in std::__shared_ptr<folly::observer_detail::Core, (__gnu_cxx::_Lock_policy)2>::~__shared_ptr() buck-out/cells/fbsource/gen/third-party/gcc/7.x/stdc++-headers#header-mode-symlink-tree-with-header-map,headers/bits/shared_ptr_base.h:1125 > #10 0x7f605833c416 in std::shared_ptr<folly::observer_detail::Core>::~shared_ptr() buck-out/cells/fbsource/gen/third-party/gcc/7.x/stdc++-headers#header-mode-symlink-tree-with-header-map,headers/bits/shared_ptr.h:93 > #11 0x7f6058376413 in folly::observer_detail::ObserverManager::scheduleRefresh(std::shared_ptr<folly::observer_detail::Core>, unsigned long)::'lambda'()::~() folly/experimental/observer/detail/ObserverManager.h:91 > #12 0x7f6058377014 in unsigned long folly::detail::function::execSmall<folly::observer_detail::ObserverManager::scheduleRefresh(std::shared_ptr<folly::observer_detail::Core>, unsigned long)::'lambda'()>(folly::detail::function::Op, folly::detail::function::Data*, folly::detail::function::Data*) folly/Function.h:592 > #13 0x7f6058377788 in folly::Function<void ()>::exec(folly::detail::function::Op, folly::detail::function::Data*, folly::detail::function::Data*) const folly/Function.h:649 > #14 0x7f6058376380 in folly::Function<void ()>::~Function() folly/Function.h:781 > #15 0x7f6058477b99 in folly::observer_detail::ObserverManager::UpdatesManager::CurrentQueue::CurrentQueue()::'lambda'()::operator()() const folly/experimental/observer/detail/ObserverManager.cpp:73 > #16 0x7f6058473de8 in void std::__invoke_impl<void, folly::observer_detail::ObserverManager::UpdatesManager::CurrentQueue::CurrentQueue()::'lambda'()>(std::__invoke_other, folly::observer_detail::ObserverManager::UpdatesManager::CurrentQueue::CurrentQueue()::'lambda'()&&) buck-out/cells/fbsource/gen/third-party/gcc/7.x/stdc++-headers#header-mode-symlink-tree-with-header-map,headers/bits/invoke.h:60 > #17 0x7f6058473c08 in std::__invoke_result<folly::observer_detail::ObserverManager::UpdatesManager::CurrentQueue::CurrentQueue()::'lambda'()>::type std::__invoke<folly::observer_detail::ObserverManager::UpdatesManager::CurrentQueue::CurrentQueue()::'lambda'()>(folly::observer_detail::ObserverManager::UpdatesManager::CurrentQueue::CurrentQueue()::'lambda'()&&) buck-out/cells/fbsource/gen/third-party/gcc/7.x/stdc++-headers#header-mode-symlink-tree-with-header-map,headers/bits/invok e.h:95 > #18 0x7f6058473b66 in decltype(std::__invoke(_S_declval<0ul>())) std::thread::_Invoker<std::tuple<folly::observer_detail::ObserverManager::UpdatesManager::CurrentQueue::CurrentQueue()::'lambda'()> >::_M_invoke<0ul>(std::_Index_tuple<0ul>) buck-out/cells/fbsource/gen/third-party/gcc/7.x/stdc++-headers#header-mode-symlink-tree-with-header-map,headers/thread:234 > #19 0x7f6058473a43 in std::thread::_Invoker<std::tuple<folly::observer_detail::ObserverManager::UpdatesManager::CurrentQueue::CurrentQueue()::'lambda'()> >::operator()() buck-out/cells/fbsource/gen/third-party/gcc/7.x/stdc++-headers#header-mode-symlink-tree-with-header-map,headers/thread:243 > #20 0x7f6058473549 in std::thread::_State_impl<std::thread::_Invoker<std::tuple<folly::observer_detail::ObserverManager::UpdatesManager::CurrentQueue::CurrentQueue()::'lambda'()> > >::_M_run() buck-out/cells/fbsource/gen/third-party/gcc/7.x/stdc++-headers#header-mode-symlink-tree-with-header-map,headers/thread:186 > #21 0x7f60576bac5f in std::execute_native_thread_routine(void*) third-party/gcc/7.x/libstdc++-v3/src/c++11/thread.cc:83 > #22 0x7f605639e6b5 in start_thread /home/engshare/third-party2/glibc/2.26/src/glibc-2.26/nptl/pthread_create.c:465:7 > #23 0x7f6055ecdebe in __GI___clone /home/engshare/third-party2/glibc/2.26/src/glibc-2.26/sysdeps/unix/sysv/linux/x86_64/clone.S:95 > > SUMMARY: UndefinedBehaviorSanitizer: unsigned-integer-overflow folly/experimental/observer/detail/Core.cpp:179:9 ``` Fix the error by rearranging increment and decrement operations. Reviewed By: leikahing Differential Revision: D19164999 fbshipit-source-id: d3c9b638492d0bf44c2acaac1e95fafe8b785182
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assign() resized the vector, but forgot to set the remaining elements to the new value.