Fix memory error in devArrMatch

[hcho3]

We recently discovered a memory error in the devArrMatch() function: https://gpuci.gpuopenanalytics.com/job/rapidsai/job/gpuci-v0.20/job/cuml/job/prb/job/cuml-gpu-test/CUDA=11.0,GPU_LABEL=gpu,OS=ubuntu16.04,PYTHON=3.7/161/console

13:09:34 [----------] 44 tests from FilTests/TreeliteDenseFilTest
13:09:34 [ RUN      ] FilTests/TreeliteDenseFilTest.Import/0
13:09:34 *** Error in `./test/ml': free(): invalid pointer: 0x00007f632b691fe8 ***
13:09:34 ======= Backtrace: =========
13:09:34 /lib/x86_64-linux-gnu/libc.so.6(+0x777f5)[0x7f632b3447f5]
13:09:34 /lib/x86_64-linux-gnu/libc.so.6(+0x8038a)[0x7f632b34d38a]
13:09:34 /lib/x86_64-linux-gnu/libc.so.6(cfree+0x4c)[0x7f632b35158c]
13:09:34 /workspace/ci/artifacts/cuml/cpu/conda_work/cpp/build/libcuml++.so(_ZN8treelite9ModelImplIffED0Ev+0xf5)[0x7f632c556405]

which was traced to the devArrMatch() function as follows:

$ valgrind ./cpp/build/test/ml --gtest_filter=FilTests/TreeliteDenseFilTest.Import/0
==6398== Mismatched free() / delete / delete []
==6398==    at 0x483D1CF: operator delete(void*, unsigned long) (in /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so)
==6398==    by 0x209287: std::_Sp_counted_base<(__gnu_cxx::_Lock_policy)2>::_M_release() (in /home/ubuntu/cuml/cpp/build/test/ml)
==6398==    by 0x2AC253: testing::AssertionResult raft::devArrMatch<float, raft::CompareApprox<float> >(float const*, float const*, unsigned long, raft::CompareApprox<float>, CUstream_st*) (in /home/ubuntu/cuml/cpp/build/test/ml)
==6398==    by 0x2AC51C: ML::BaseFilTest::compare() (in /home/ubuntu/cuml/cpp/build/test/ml)
==6398==    by 0x4858098D: void testing::internal::HandleExceptionsInMethodIfSupported<testing::Test, void>(testing::Test*, void (testing::Test::*)(), char const*) (in /home/ubuntu/miniconda3/envs/cuml_dev/lib/libgtest.so)
==6398==    by 0x48580BE0: testing::Test::Run() (in /home/ubuntu/miniconda3/envs/cuml_dev/lib/libgtest.so)
==6398==    by 0x48580F0E: testing::TestInfo::Run() (in /home/ubuntu/miniconda3/envs/cuml_dev/lib/libgtest.so)
==6398==    by 0x48581035: testing::TestSuite::Run() (in /home/ubuntu/miniconda3/envs/cuml_dev/lib/libgtest.so)
==6398==    by 0x485815EB: testing::internal::UnitTestImpl::RunAllTests() (in /home/ubuntu/miniconda3/envs/cuml_dev/lib/libgtest.so)
==6398==    by 0x48581858: testing::UnitTest::Run() (in /home/ubuntu/miniconda3/envs/cuml_dev/lib/libgtest.so)
==6398==    by 0x4853007E: main (in /home/ubuntu/miniconda3/envs/cuml_dev/lib/libgtest_main.so)
==6398==  Address 0x232bfa860 is 0 bytes inside a block of size 160,000 alloc'd
==6398==    at 0x483C583: operator new[](unsigned long) (in /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so)
==6398==    by 0x2ABFF8: testing::AssertionResult raft::devArrMatch<float, raft::CompareApprox<float> >(float const*, float const*, unsigned long, raft::CompareApprox<float>, CUstream_st*) (in /home/ubuntu/cuml/cpp/build/test/ml)
==6398==    by 0x2AC51C: ML::BaseFilTest::compare() (in /home/ubuntu/cuml/cpp/build/test/ml)
==6398==    by 0x4858098D: void testing::internal::HandleExceptionsInMethodIfSupported<testing::Test, void>(testing::Test*, void (testing::Test::*)(), char const*) (in /home/ubuntu/miniconda3/envs/cuml_dev/lib/libgtest.so)
==6398==    by 0x48580BE0: testing::Test::Run() (in /home/ubuntu/miniconda3/envs/cuml_dev/lib/libgtest.so)
==6398==    by 0x48580F0E: testing::TestInfo::Run() (in /home/ubuntu/miniconda3/envs/cuml_dev/lib/libgtest.so)
==6398==    by 0x48581035: testing::TestSuite::Run() (in /home/ubuntu/miniconda3/envs/cuml_dev/lib/libgtest.so)
==6398==    by 0x485815EB: testing::internal::UnitTestImpl::RunAllTests() (in /home/ubuntu/miniconda3/envs/cuml_dev/lib/libgtest.so)
==6398==    by 0x48581858: testing::UnitTest::Run() (in/home/ubuntu/miniconda3/envs/cuml_dev/lib/libgtest.so)
==6398==    by 0x4853007E: main (in /home/ubuntu/miniconda3/envs/cuml_dev/lib/libgtest_main.so)

Diagnosis. The devArrMatch functions are allocating a temporary buffer using new[] and then assigning it to a shared_ptr<T>. This is not valid because the destructor of shared_ptr<T> will invoke delete, not delete[]. Calling delete with a buffer allocated by new[] leads to an undefined behavior. See https://docs.microsoft.com/en-us/cpp/code-quality/c6278?view=msvc-160.

Proposed fix. Use std:unique_ptr<T[]> instead to store temporary buffers.

[hcho3]

Note to myself: devArrMatch() is duplicated in cpp/test/prims/test_utils.h of cuML. Will need to make the same fix there too.

[hcho3]

I updated the PR to use std:unique_ptr<T[]> instead, since T can be a boolean and std::vector<bool> is a special container where you cannot take address of individual elements.

[cjnolet]

LGTM pending CI.

[dantegd]

@gpucibot merge

[hcho3]

@dantegd @cjnolet How do we bring in the latest RAFT into cuML? rapidsai/cuml#3855 is blocked by the memory error.

[cjnolet]

@hcho3, replace the git commit hash for RAFT in cpp/cmake/Dependencies.cmake

[hcho3]

Thanks!