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https://issues.apache.org/jira/browse/ARROW-13812?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17407629#comment-17407629
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David Li commented on ARROW-13812:
----------------------------------
So what's going on here took me a while to unwind, but:
* We're generating the array of unique values for a bool.
* Ultimately this happens in BitUtil::bytes_to_bits. This reads 8 bytes and
packs them into one byte.
* The buffer it reads is generated by EncoderInteger::Decode. This writes data
into a buffer given to it.
* The buffer given to it ultimately stems from a TempVectorStack, whose memory
is not initialized.
And in this test case, we're generating an array of 3 bools. So from Valgrind's
perspective, we're taking 3 bytes and 5 garbage bytes and packing it into one
garbage byte. I think the solution should be to always round up to 8 bytes.
> [C++] Valgrind failure in Grouper.BooleanKey (uninitialized values)
> -------------------------------------------------------------------
>
> Key: ARROW-13812
> URL: https://issues.apache.org/jira/browse/ARROW-13812
> Project: Apache Arrow
> Issue Type: Bug
> Components: C++
> Reporter: David Li
> Assignee: David Li
> Priority: Major
> Labels: query-engine
> Fix For: 6.0.0
>
>
> From the
> [nightlies|https://dev.azure.com/ursacomputing/crossbow/_build/results?buildId=10785&view=logs&j=0da5d1d9-276d-5173-c4c4-9d4d4ed14fdb&t=d9b15392-e4ce-5e4c-0c8c-b69645229181&l=4978].
> {noformat}
> [ RUN ] Grouper.BooleanKey
> ==11849== Conditional jump or move depends on uninitialised value(s)
> ==11849== at 0x4122555: arrow::TestInitialized(arrow::ArrayData const&)
> (gtest_util.cc:675)
> ==11849== by 0x431604: arrow::compute::(anonymous
> namespace)::ValidateOutput(arrow::ArrayData const&) (test_util.cc:202)
> ==11849== by 0x431F94: arrow::compute::ValidateOutput(arrow::Datum const&)
> (test_util.cc:235)
> ==11849== by 0x40010B:
> arrow::compute::TestGrouper::ValidateConsume(arrow::compute::ExecBatch
> const&, arrow::Datum const&) (hash_aggregate_test.cc:380)
> ==11849== by 0x400C03:
> arrow::compute::TestGrouper::ConsumeAndValidate(arrow::compute::ExecBatch
> const&, arrow::Datum*) (hash_aggregate_test.cc:364)
> ==11849== by 0x410BD5: ExpectConsume (hash_aggregate_test.cc:318)
> ==11849== by 0x410BD5:
> arrow::compute::TestGrouper::ExpectConsume(std::__cxx11::basic_string<char,
> std::char_traits<char>, std::allocator<char> > const&,
> std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>
> > const&) (hash_aggregate_test.cc:307)
> ==11849== by 0x410F74: arrow::compute::Grouper_BooleanKey_Test::TestBody()
> (hash_aggregate_test.cc:415)
> ==11849== by 0x5D7398D: void
> testing::internal::HandleExceptionsInMethodIfSupported<testing::Test,
> void>(testing::Test*, void (testing::Test::*)(), char const*) (in
> /opt/conda/envs/arrow/lib/libgtest.so)
> ==11849== by 0x5D73BE0: testing::Test::Run() (in
> /opt/conda/envs/arrow/lib/libgtest.so)
> ==11849== by 0x5D73F0E: testing::TestInfo::Run() (in
> /opt/conda/envs/arrow/lib/libgtest.so)
> ==11849== by 0x5D74035: testing::TestSuite::Run() (in
> /opt/conda/envs/arrow/lib/libgtest.so)
> ==11849== by 0x5D745EB: testing::internal::UnitTestImpl::RunAllTests() (in
> /opt/conda/envs/arrow/lib/libgtest.so)
> ==11849== by 0x5D74858: testing::UnitTest::Run() (in
> /opt/conda/envs/arrow/lib/libgtest.so)
> ==11849== by 0x421207E: main (in
> /opt/conda/envs/arrow/lib/libgtest_main.so)
> ==11849==
> {
> <insert_a_suppression_name_here>
> Memcheck:Cond
> fun:_ZN5arrow15TestInitializedERKNS_9ArrayDataE
> fun:_ZN5arrow7compute12_GLOBAL__N_114ValidateOutputERKNS_9ArrayDataE
> fun:_ZN5arrow7compute14ValidateOutputERKNS_5DatumE
>
> fun:_ZN5arrow7compute11TestGrouper15ValidateConsumeERKNS0_9ExecBatchERKNS_5DatumE
>
> fun:_ZN5arrow7compute11TestGrouper18ConsumeAndValidateERKNS0_9ExecBatchEPNS_5DatumE
> fun:ExpectConsume
>
> fun:_ZN5arrow7compute11TestGrouper13ExpectConsumeERKNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEES9_
> fun:_ZN5arrow7compute23Grouper_BooleanKey_Test8TestBodyEv
>
> fun:_ZN7testing8internal35HandleExceptionsInMethodIfSupportedINS_4TestEvEET0_PT_MS4_FS3_vEPKc
> fun:_ZN7testing4Test3RunEv
> fun:_ZN7testing8TestInfo3RunEv
> fun:_ZN7testing9TestSuite3RunEv
> fun:_ZN7testing8internal12UnitTestImpl11RunAllTestsEv
> fun:_ZN7testing8UnitTest3RunEv
> fun:main
> } {noformat}
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