On Sun, Jan 28, 2024 at 3:18 PM Knut Stolze <[email protected]> wrote:
> Hello folks! > > Just the other day, we run into a problem in our C++ project, which we > tracked down to static initialization order fiasco. Specifically, we have a > global variable/constant container, which includes elements that have a > proto object container a map. https://godbolt.org/z/49Mx6h7Yz > > What happened is that the global variable "store_t::m_map" is initialized > first. The stack trace shows that the code in protobuf > UntypedMapBase::TableEntryIsNonEmptyList() gets executed. > ==275==ERROR: ThreadSanitizer: SEGV on unknown address 0x0001c8c56070 (pc > 0x7f347b67db2a bp 0x7ffdd006baf0 sp 0x7ffdd006ba90 T275) ==275==The signal > is caused by a READ memory access. #0 > google::protobuf::internal::UntypedMapBase::TableEntryIsNonEmptyList(unsigned > long) const > bazel-out/k8-dbg/bin/external/com_google_protobuf/src/google/protobuf/_virtual_includes/protobuf_lite/google/protobuf/map.h:514 > #1 google::protobuf::internal::UntypedMapBase::NodeAndBucket > google::protobuf::internal::KeyMapBase<std::__cxx11::basic_string<char, > std::char_traits<char>, std::allocator<char> > >::FindHelper<char > const*>(char const* const&, > absl::container_internal::btree_iterator<absl::container_internal::btree_node<absl::container_internal::map_params<std::reference_wrapper<std::__cxx11::basic_string<char, > std::char_traits<char>, std::allocator<char> > const>, > google::protobuf::internal::NodeBase*, > google::protobuf::internal::TransparentSupport<std::__cxx11::basic_string<char, > std::char_traits<char>, std::allocator<char> > >::less, > google::protobuf::internal::MapAllocator<std::pair<std::reference_wrapper<std::__cxx11::basic_string<char, > std::char_traits<char>, std::allocator<char> > const> const, > google::protobuf::internal::NodeBase*> >, 256, false> >, > std::pair<std::reference_wrapper<std::__cxx11::basic_string<char, > std::char_traits<char>, std::allocator<char> > const> const, > google::protobuf::internal::NodeBase*>&, > std::pair<std::reference_wrapper<std::__cxx11::basic_string<char, > std::char_traits<char>, std::allocator<char> > const> const, > google::protobuf::internal::NodeBase*>*>*) const > bazel-out/k8-dbg/bin/external/com_google_protobuf/src/google/protobuf/_virtual_includes/protobuf_lite/google/protobuf/map.h:767 > #2 std::pair<google::protobuf::Map<std::__cxx11::basic_string<char, > std::char_traits<char>, std::allocator<char> >, > md::redundancyType>::iterator, bool> > google::protobuf::Map<std::__cxx11::basic_string<char, > std::char_traits<char>, std::allocator<char> >, > md::redundancyType>::TryEmplaceInternal<char const* const&>(char const* > const&) > bazel-out/k8-dbg/bin/external/com_google_protobuf/src/google/protobuf/_virtual_includes/protobuf_lite/google/protobuf/map.h:1463 > #3 std::pair<google::protobuf::Map<std::__cxx11::basic_string<char, > std::char_traits<char>, std::allocator<char> >, > md::redundancyType>::iterator, bool> > google::protobuf::Map<std::__cxx11::basic_string<char, > std::char_traits<char>, std::allocator<char> >, > md::redundancyType>::ArenaAwareTryEmplace<char const* > const&>(std::integral_constant<bool, false>, char const* const&) > bazel-out/k8-dbg/bin/external/com_google_protobuf/src/google/protobuf/_virtual_includes/protobuf_lite/google/protobuf/map.h:1532 > #4 std::pair<google::protobuf::Map<std::__cxx11::basic_string<char, > std::char_traits<char>, std::allocator<char> >, > md::redundancyType>::iterator, bool> > google::protobuf::Map<std::__cxx11::basic_string<char, > std::char_traits<char>, std::allocator<char> >, > md::redundancyType>::try_emplace<char const* const&>(char const* const&) > bazel-out/k8-dbg/bin/external/com_google_protobuf/src/google/protobuf/_virtual_includes/protobuf_lite/google/protobuf/map.h:1300 > #5 md::redundancyType& > google::protobuf::Map<std::__cxx11::basic_string<char, > std::char_traits<char>, std::allocator<char> >, > md::redundancyType>::operator[]<char const*>(char const* const&) > bazel-out/k8-dbg/bin/external/com_google_protobuf/src/google/protobuf/_virtual_includes/protobuf_lite/google/protobuf/map.h:1222 > #6 info_t::constructTI() src/info.cpp:62 #7 info_t::info_t(int) > src/info.cpp:23 #8 __static_initialization_and_destruction_0 store.cpp:37 > This sigsegv happens if "kGlobalEmptyTable" in protobuf/map.cc was not yet > initialized and an invalid pointer is dereferenced in > UntypedMapBase::TableEntryIsNonEmptyList(). > > I'd like to submit a patch that move the global variable definition inside > a function, i.e.a a block-scope variable with static storage duration. I'd > also use an std::array to define "kGlobalEmptyTable". Are there any > concerns with doing this? > kGlobalEmptyTable has a constant initializer. It does not need any runtime initialization and should not cause "static initialization order fiasco". Even if it was dynamically initialized, it is a static storage variable so it is zero initialized before the program starts, and the zero initialization is exactly the state we want it to have. I suspect the bug is elsewhere. However, it is important to note that protobuf use before main() is best effort and generally not supported. I see you are running with thread sanitizer. Have you tried using address sanitizer? ASan will diagnose "static initialization order fiasco" errors explicitly. https://github.com/google/sanitizers/wiki/AddressSanitizerInitializationOrderFiasco > > Regards, > Knut Stolze > > -- > You received this message because you are subscribed to the Google Groups > "Protocol Buffers" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/protobuf/b63ec52c-059d-442b-9b17-061f3da469a1n%40googlegroups.com > <https://groups.google.com/d/msgid/protobuf/b63ec52c-059d-442b-9b17-061f3da469a1n%40googlegroups.com?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "Protocol Buffers" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. 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