Details
Critical Description
The regression MDEV-33972 was only caught in a rather obscure way: a bit of an unrelated pointer was being cleared, because some code was dereferencing an invalid iterator.
It turns out that there is a simple way to enable debugging for the iterators defined in the GNU libstdc++:
diff --git a/storage/innobase/CMakeLists.txt b/storage/innobase/CMakeLists.txt
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index 5f01f8c9704..bccf81a6b5b 100644
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--- a/storage/innobase/CMakeLists.txt
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+++ b/storage/innobase/CMakeLists.txt
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@@ -78,7 +78,7 @@ ADD_FEATURE_INFO(INNODB_ROOT_GUESS WITH_INNODB_ROOT_GUESS
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OPTION(WITH_INNODB_EXTRA_DEBUG "Enable extra InnoDB debug checks" OFF)
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IF(WITH_INNODB_EXTRA_DEBUG)
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- ADD_DEFINITIONS(-DUNIV_ZIP_DEBUG -DLOG_LATCH_DEBUG)
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+ ADD_DEFINITIONS(-DUNIV_ZIP_DEBUG -DLOG_LATCH_DEBUG -D_GLIBCXX_DEBUG)
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ENDIF()
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ADD_FEATURE_INFO(INNODB_EXTRA_DEBUG WITH_INNODB_EXTRA_DEBUG "Extra InnoDB debug checks")
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However, this has no effect on the clang libc++, which is a prerequisite for MemorySanitizer builds (MDEV-20377). There used to be -D_LIBCPP_DEBUG, but it has been split into multiple flags:
diff --git a/libcxx/include/__assert b/libcxx/include/__assert
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index d94a657aac50..e20ee50b127c 100644
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--- a/libcxx/include/__assert
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+++ b/libcxx/include/__assert
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@@ -17,11 +17,6 @@
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# pragma GCC system_header
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#endif
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-// TODO: Remove in LLVM 17.
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-#if defined(_LIBCPP_DEBUG)
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-# error "Defining _LIBCPP_DEBUG is not supported anymore. Please use _LIBCPP_ENABLE_DEBUG_MODE instead."
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-#endif
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-
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// Automatically enable assertions when the debug mode is enabled.
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#if defined(_LIBCPP_ENABLE_DEBUG_MODE)
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# ifndef _LIBCPP_ENABLE_ASSERTIONS |
I did not have any luck with that flag either. The libstdc++ flag works:
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10.11 f0d0ddc992703f2d31d8ad0d963f127a8b4d05e9 |
/usr/bin/../lib/gcc/x86_64-linux-gnu/14/../../../../include/c++/14/debug/safe_iterator.h:372:
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In function:
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pointer
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gnu_debug::_Safe_iterator<std::_Rb_tree_iterator<std::pair<dict_table_t
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*const, trx_mod_table_time_t>>, std::map<dict_table_t *,
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trx_mod_table_time_t, std::less<dict_table_t *>,
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ut_allocator<std::pair<dict_table_t *const, trx_mod_table_time_t>>>,
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std::forward_iterator_tag>::operator->() const [_Iterator =
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std::_Rb_tree_iterator<std::pair<dict_table_t *const,
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trx_mod_table_time_t>>, _Sequence = std::map<dict_table_t *,
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trx_mod_table_time_t, std::less<dict_table_t *>,
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ut_allocator<std::pair<dict_table_t *const, trx_mod_table_time_t>>>,
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_Category = std::forward_iterator_tag]
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Error: attempt to dereference a past-the-end iterator.
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Objects involved in the operation:
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iterator "this" @ 0x7fb892ffd7a8 {
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type = std::_Rb_tree_iterator<std::pair<dict_table_t* const, trx_mod_table_time_t> > (mutable iterator);
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state = past-the-end;
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references sequence with type 'std::debug::map<dict_table_t*, trx_mod_table_time_t, std::less<dict_table_t*>, ut_allocator<std::pair<dict_table_t* const, trx_mod_table_time_t>, true> >' @ 0x7fb8918016b0
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}
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240423 14:07:36 [ERROR] mysqld got signal 6 ;
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I would prefer something like the following to cover all use of iterators:
diff --git a/CMakeLists.txt b/CMakeLists.txt
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index 6477c4042d6..e0d73899632 100644
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--- a/CMakeLists.txt
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+++ b/CMakeLists.txt
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@@ -277,7 +277,14 @@ ENDIF()
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# Always enable debug sync for debug builds.
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SET(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} -DENABLED_DEBUG_SYNC")
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SET(CMAKE_C_FLAGS_DEBUG "${CMAKE_C_FLAGS_DEBUG} -DENABLED_DEBUG_SYNC")
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-
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+
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+IF(MSVC)
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+ SET(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} -D_ITERATOR_DEBUG_LEVEL=1")
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+ELSE()
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+ # Enable extra checks on GNU libstdc++ iterators
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+ SET(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} -D_GLIBCXX_DEBUG")
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+ENDIF()
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+
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OPTION(ENABLE_GCOV "Enable gcov (debug, Linux builds only)" OFF)
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IF (ENABLE_GCOV)
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MY_CHECK_AND_SET_COMPILER_FLAG("-DHAVE_gcov -fprofile-arcs -ftest-coverage -lgcov" DEBUG) |
Unfortunately it would cause link-time failures like this:
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10.11 f0d0ddc992703f2d31d8ad0d963f127a8b4d05e9 |
ld.lld: error: undefined symbol: wsrep::client_state::enter_toi_local(std::__debug::vector<wsrep::key, std::allocator<wsrep::key>> const&, wsrep::const_buffer const&, std::chrono::time_point<std::chrono::_V2::steady_clock, std::chrono::duration<long, std::ratio<1l, 1000000000l>>>)
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>>> referenced by wsrep_mysqld.cc:2794 (/mariadb/10.11/sql/wsrep_mysqld.cc:2794)
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>>> wsrep_mysqld.cc.o:(wsrep_TOI_begin(THD*, char const*, char const*, TABLE_LIST const*, Alter_info const*, std::__debug::vector<wsrep::key, std::allocator<wsrep::key>> const*, HA_CREATE_INFO const*)) in archive sql/libwsrep.a
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I see that wsrep-lib/CMakeLists.txt is doing something to the project-wide CMAKE_CXX_FLAGS; this might be the reason.
Attachments
Issue Links
- relates to
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MDEV-33972 Memory corruption in innodb.insert_into_empty
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- Closed
-