cudf: [BUG] TYPES_TEST failure with gcc7.3

During Build, I have observed build failure with commit - c81152e424871b5f00a777d6bca6ccde3301f536 Build log snippet:

ll/include -I$BUILD_PREFIX/include -I$SRC_DIR/cpp/build/include -I$SRC_DIR/cpp/include -I$SRC_DIR/cpp -I$SRC_DIR/cpp/src -I$SRC_DIR/cpp/thirdparty/cub -I$SRC_DIR/cpp/thirdparty/jitify -I$SRC_DIR/cpp/thirdparty/dlpack/include -I$SRC_DIR/cpp/build/arrow/install/include -I$SRC_DIR/cpp/build/arrow/build/flatbuffers_ep-prefix/src/flatbuffers_ep-install/include -I$PREFIX/include  -fvisibility-inlines-hidden  -fmessage-length=0 -mcpu=power8 -mtune=power8 -mpower8-fusion -mpower8-vector -ftree-vectorize -fPIC -fstack-protector-strong -fno-plt -O3 -pipe -I$PREFIX/include -fdebug-prefix-map=$SRC_DIR=/usr/local/src/conda/libcudf-0.7.0.dev0 -fdebug-prefix-map=$PREFIX=/usr/local/src/conda-prefix -Werror -O3 -DNDEBUG -fPIE   -std=gnu++14 -o CMakeFiles/TYPES_TEST.dir/types/types_test.cpp.o -c $SRC_DIR/cpp/tests/types/types_test.cpp
/work/cpp/tests/types/types_test.cpp: In member function 'virtual void WrappersTestBool8_BooleanOperatorsBool8_Test::TestBody()':

/work/cpp/tests/types/types_test.cpp:243:23: error: narrowing conversion of '-42' from 'int' to 'char' inside { } [-Wnarrowing]
     cudf::bool8 w4{-42};
                       ^
/work/cpp/tests/types/types_test.cpp: In member function 'virtual void WrappersTestBool8_CastArithmeticTest_Test::TestBody()':
/opt/anaconda3/conda-bld/libcudf_1556628699139/work/cpp/tests/types/types_test.cpp:276:23: error: narrowing conversion of '-42' from 'int' to 'char' inside { } [-Wnarrowing]
     cudf::bool8 w2{-42};
                       ^

I have added -Wno-narrowing in cpp/CMakeLists.txt and able to build with the change. However I can see test failures -

      Start 20: TYPES_TEST
20/29 Test #20: TYPES_TEST .......................***Failed    2.49 sec

Detailed Log for the failures-

[       OK ] WrappersTest/0.UnwrapFundamentalTest (0 ms)
[ RUN      ] WrappersTest/0.ArithmeticOperators
[       OK ] WrappersTest/0.ArithmeticOperators (1 ms)
[ RUN      ] WrappersTest/0.CompoundAssignmentOperators
/opt/anaconda3/conda-bld/libcudf_1556630025815/work/cpp/tests/types/types_test.cpp:313: Failure
      Expected: t0
      Which is: 3
To be equal to: static_cast<UnderlyingType>(w0.value)
      Which is: 209652396
/opt/anaconda3/conda-bld/libcudf_1556630025815/work/cpp/tests/types/types_test.cpp:313: Failure
      Expected: t0
      Which is: 0
To be equal to: static_cast<UnderlyingType>(w0.value)
      Which is: 924231285
/opt/anaconda3/conda-bld/libcudf_1556630025815/work/cpp/tests/types/types_test.cpp:313: Failure
      Expected: t0
      Which is: 0
To be equal to: static_cast<UnderlyingType>(w0.value)
      Which is: 441365315
/opt/anaconda3/conda-bld/libcudf_1556630025815/work/cpp/tests/types/types_test.cpp:313: Failure
      Expected: t0
      Which is: 0
To be equal to: static_cast<UnderlyingType>(w0.value)
      Which is: 192771779
/opt/anaconda3/conda-bld/libcudf_1556630025815/work/cpp/tests/types/types_test.cpp:313: Failure
      Expected: t0
      Which is: 2
To be equal to: static_cast<UnderlyingType>(w0.value)
      Which is: -327900151
/opt/anaconda3/conda-bld/libcudf_1556630025815/work/cpp/tests/types/types_test.cpp:313: Failure
      Expected: t0
      Which is: 1
To be equal to: static_cast<UnderlyingType>(w0.value)
      Which is: 626610453

Please suggest if this is already a known issue. Thank you !