Info

Immer incorrectly assumes GCC does not support exceptions, because it's checking a clang-specific feature macro. Furthermore, with optimization turned off, its IMMER_RETHROW empty definition yields a function missing a return statement, a fatal build warning for us. Scons script and output attached. Essentially this scons invocation: $ python3-venv/bin/python3 \ buildscripts/scons.py \ VARIANT_DIR=enterprise_dynamic_gcc_gdb_noopt_asan \ LLVM_SYMBOLIZER=/opt/mongodbtoolchain/v4/bin/llvm-symbolizer \ VERBOSE=1 \ LIBS=rt \ --variables-files=etc/scons/mongodbtoolchain_stable_gcc.vars \ --sanitize=address \ --allocator=system \ --link-model=dynamic \ --opt=off \ build/enterprise_dynamic_gcc_gdb_noopt_asan/mongo/db/catalog/historical_catalogid_tracker.dyn.o Yields a series of fatal warnings: /opt/mongodbtoolchain/v4/bin/g++ -o build/enterprise_dynamic_gcc_gdb_noopt_asan/mongo/db/catalog/historical_catalogid_tracker.dyn.o -c -Woverloaded-virtual -Wpessimizing-move -Wno-maybe-uninitialized -fsized-deallocation -std=c++20 -Werror -include mongo/platform/basic.h -ffp-contract=off -fasynchronous-unwind-tables -g2 -Wall -Wsign-compare -Wno-unknown-pragmas -Winvalid-pch -gdwarf-5 -fno-omit-frame-pointer -fno-strict-aliasing -O0 -march=sandybridge -mtune=generic -mprefer-vector-width=128 -Wno-unused-local-typedefs -Wno-unused-function -Wno-deprecated-declarations -Wno-unused-const-variable -Wno-unused-but-set-variable -Wno-missing-braces -Wno-psabi -fstack-protector-strong -fsanitize=address -fno-omit-frame-pointer -gdwarf32 -Wa,--nocompress-debug-sections -fno-builtin-memcmp -Wimplicit-fallthrough=5 -fPIC -DSAFEINT_USE_INTRINSICS=0 -DPCRE2_STATIC -DMONGO_USE_VISIBILITY -DNDEBUG -D_XOPEN_SOURCE=700 -D_GNU_SOURCE -DADDRESS_SANITIZER -DABSL_FORCE_ALIGNED_ACCESS -DBOOST_ENABLE_ASSERT_DEBUG_HANDLER -DBOOST_FILESYSTEM_NO_CXX20_ATOMIC_REF -DBOOST_LOG_NO_SHORTHAND_NAMES -DBOOST_LOG_USE_NATIVE_SYSLOG -DBOOST_LOG_WITHOUT_THREAD_ATTR -DBOOST_MATH_NO_LONG_DOUBLE_MATH_FUNCTIONS -DBOOST_SYSTEM_NO_DEPRECATED -DBOOST_THREAD_USES_DATETIME -DBOOST_THREAD_VERSION=5 -DBOOST_LOG_DYN_LINK -Isrc/third_party/s2 -Isrc/third_party/variant-1.4.0/include -Isrc/third_party/libstemmer_c/include -Isrc/third_party/SafeInt -Isrc/third_party/murmurhash3 -Isrc/third_party/immer/dist -Isrc/third_party/fmt/dist/include -Isrc/third_party/boost -Isrc/third_party/abseil-cpp/dist -Ibuild/enterprise_dynamic_gcc_gdb_noopt_asan -Isrc src/mongo/db/catalog/historical_catalogid_tracker.cpp In file included from src/third_party/immer/dist/immer/map.hpp:12, from src/mongo/util/immutable/unordered_map.h:32, from src/mongo/db/catalog/historical_catalogid_tracker.h:34, from src/mongo/db/catalog/historical_catalogid_tracker.cpp:30: src/third_party/immer/dist/immer/detail/hamts/champ.hpp: In member function 'immer::detail::hamts::champ::add_result immer::detail::hamts::champ::do_add(immer::detail::hamts::champ::node_t*, T, immer::detail::hamts::hash_t, immer::detail::hamts::shift_t) const [with T = mongo::NamespaceString; Hash = absl::lts_20211102::hash_internal::Hash; Equal = std::equal_to; MemoryPolicy = immer::memory_policy, immer::refcount_policy, void, immer::no_transience_policy, true, true>; unsigned int B = 5]': src/third_party/immer/dist/immer/detail/hamts/champ.hpp:620:5: error: control reaches end of non-void function [-Werror=return-type] 620 | } | ^

Top User Comments

xgen-internal-githook commented on Thu, 18 Jan 2024 05:08:57 +0000: Author: {'name': 'Henrik Edin', 'email': 'henrik.edin@mongodb.com', 'username': 'henrikedin'} Message: SERVER-77694 Import immer lib from fork containing fix to always enable exceptions (cherry picked from commit 016bb8a5ecc4b91e0a6fdcc58d0ff66c238fa970) GitOrigin-RevId: b1eaa84c50588356f31c6da736f8dee2f2d5e26a Branch: v5.0 https://github.com/mongodb/mongo/commit/1c426ee44ad16caa8c5ccd79edebe41a213a9238 xgen-internal-githook commented on Wed, 17 Jan 2024 21:45:48 +0000: Author: {'name': 'Henrik Edin', 'email': 'henrik.edin@mongodb.com', 'username': 'henrikedin'} Message: SERVER-77694 Import immer lib from fork containing fix to always enable exceptions (cherry picked from commit 016bb8a5ecc4b91e0a6fdcc58d0ff66c238fa970) GitOrigin-RevId: 8651ee570081d7fa33a44a53207494a4d390fcdf Branch: v6.0 https://github.com/mongodb/mongo/commit/fb8ba242265f6443653d170aadd84c7e86375cc4 billy.donahue commented on Mon, 26 Jun 2023 15:05:56 +0000: Our upstream issue report received a response. Created SERVER-78430 as dependent on this ticket, to track the creation of a long-term and upstreamable fix for this problem. xgen-internal-githook commented on Wed, 7 Jun 2023 14:35:58 +0000: Author: {'name': 'Henrik Edin', 'email': 'henrik.edin@mongodb.com', 'username': 'henrikedin'} Message: SERVER-77694 Import immer lib from fork containing fix to always enable exceptions (cherry picked from commit 016bb8a5ecc4b91e0a6fdcc58d0ff66c238fa970) Branch: v7.0 https://github.com/mongodb/mongo/commit/a5abe1945467aafab256a3788bfe0fb25fa3f24c xgen-internal-githook commented on Tue, 6 Jun 2023 15:43:08 +0000: Author: {'name': 'Henrik Edin', 'email': 'henrik.edin@mongodb.com', 'username': 'henrikedin'} Message: SERVER-77694 Import immer lib from fork containing fix to always enable exceptions Branch: master https://github.com/mongodb/mongo/commit/016bb8a5ecc4b91e0a6fdcc58d0ff66c238fa970 billy.donahue commented on Thu, 1 Jun 2023 19:57:34 +0000: Opened bug with upstream just about the IMMER_RETHROW. The exception detection is also broken and need another upstream ticket, I think. https://github.com/arximboldi/immer/issues/264 billy.donahue commented on Thu, 1 Jun 2023 19:10:56 +0000: henrik.edin@mongodb.com feel free to reassign. I only named you because you'll know who owns this . billy.donahue commented on Thu, 1 Jun 2023 18:59:04 +0000: Idea: maybe IMMER_RETHROW should be __builtin_unreachable() or similar if exceptions are disabled. https://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html#index-_005f_005fbuiltin_005funreachable or into a call to any function marked [[noreturn]], such as std::terminate, which is a portable solution. billy.donahue commented on Thu, 1 Jun 2023 18:31:52 +0000: https://mongodb.slack.com/archives/CQDQ9R413/p1685640114769829 Bottom line seems to be that there are two different immer bugs at work here. incorrect detection of exception support, yielding failure to detect exception support in gcc. IMMER_RETHROW looks like a function falling off the end without a return statement when exceptions are disabled. As a result, it appears that the immer library will behave drastically differently on clang vs gcc. On clang builds it will be exception-based but on gcc builds the same code paths will kill the server.

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