[REVIEW] fix gcc-9 compilation error

[rongou]

The std::move() call prevents copy elision:

/home/rou/src/cudf/cpp/src/dictionary/remove_keys.cu: In instantiation of ‘std::unique_ptr<cudf::column> cudf::dictionary::detail::_GLOBAL__N__46_tmpxft_00004b4a_00000000_7_remove_keys_cpp1_ii_8f7b9da6::remove_keys_fn(const cudf::dictionary_column_view&, KeysKeeper, rmm::mr::device_memory_resource*, cudaStream_t) [with KeysKeeper = __nv_dl_wrapper_t<__nv_dl_tag<std::unique_ptr<cudf::column> (*)(const cudf::dictionary_column_view&, const cudf::column_view&, rmm::mr::device_memory_resource*, CUstream_st*), cudf::dictionary::detail::remove_keys, 1>, const bool*>; cudaStream_t = CUstream_st*]’:
/home/rou/src/cudf/cpp/src/dictionary/remove_keys.cu:160:65:   required from here
/home/rou/src/cudf/cpp/src/dictionary/remove_keys.cu:83:27: error: moving a local object in a return statement prevents copy elision [-Werror=pessimizing-move]
   83 |       return std::move(positions);
      |                           ^
/home/rou/src/cudf/cpp/src/dictionary/remove_keys.cu:83:27: note: remove ‘std::move’ call
/home/rou/src/cudf/cpp/src/dictionary/remove_keys.cu: In instantiation of ‘std::unique_ptr<cudf::column> cudf::dictionary::detail::_GLOBAL__N__46_tmpxft_00004b4a_00000000_7_remove_keys_cpp1_ii_8f7b9da6::remove_keys_fn(const cudf::dictionary_column_view&, KeysKeeper, rmm::mr::device_memory_resource*, cudaStream_t) [with KeysKeeper = __nv_dl_wrapper_t<__nv_dl_tag<std::unique_ptr<cudf::column> (*)(const cudf::dictionary_column_view&, rmm::mr::device_memory_resource*, CUstream_st*), cudf::dictionary::detail::remove_unused_keys, 1>, const bool*>; cudaStream_t = CUstream_st*]’:
/home/rou/src/cudf/cpp/src/dictionary/remove_keys.cu:186:65:   required from here
/home/rou/src/cudf/cpp/src/dictionary/remove_keys.cu:83:27: error: moving a local object in a return statement prevents copy elision [-Werror=pessimizing-move]
/home/rou/src/cudf/cpp/src/dictionary/remove_keys.cu:83:27: note: remove ‘std::move’ call
cc1plus: all warnings being treated as errors
CMakeFiles/cudf.dir/build.make:2668: recipe for target 'CMakeFiles/cudf.dir/src/dictionary/remove_keys.cu.o' failed
make[2]: *** [CMakeFiles/cudf.dir/src/dictionary/remove_keys.cu.o] Error 1
CMakeFiles/Makefile2:230: recipe for target 'CMakeFiles/cudf.dir/all' failed
make[1]: *** [CMakeFiles/cudf.dir/all] Error 2
Makefile:148: recipe for target 'all' failed
make: *** [all] Error 2

@davidwendt @jrhemstad @kkraus14

[GPUtester]

Can one of the admins verify this patch?

[GPUtester]

Please update the changelog in order to start CI tests.

View the gpuCI docs here.

[devavret]

Github shows only 1 line changed. And that's the changelog. Where's the code?

[rongou]

Ah I was trying to reproduce the error.

[codecov]

Codecov Report

Merging #6298 into branch-0.16 will increase coverage by 0.28%.
The diff coverage is n/a.

@@               Coverage Diff               @@
##           branch-0.16    #6298      +/-   ##
===============================================
+ Coverage        84.45%   84.74%   +0.28%     
===============================================
  Files               82       82              
  Lines            13846    14176     +330     
===============================================
+ Hits             11694    12013     +319     
- Misses            2152     2163      +11     

Impacted Files	Coverage Δ
python/dask_cudf/dask_cudf/io/parquet.py	91.35% <0.00%> (-0.85%)	⬇️
python/cudf/cudf/_version.py	44.80% <0.00%> (-0.72%)	⬇️
python/cudf/cudf/io/parquet.py	91.73% <0.00%> (-0.50%)	⬇️
python/cudf/cudf/core/series.py	90.96% <0.00%> (-0.37%)	⬇️
python/cudf/cudf/utils/applyutils.py	98.74% <0.00%> (-0.01%)	⬇️
python/cudf/cudf/utils/ioutils.py	85.84% <0.00%> (ø)
python/cudf/cudf/utils/docutils.py	100.00% <0.00%> (ø)
python/dask_cudf/dask_cudf/io/csv.py	95.52% <0.00%> (ø)
python/cudf/cudf/core/column/string.py	86.05% <0.00%> (ø)
python/dask_cudf/dask_cudf/io/tests/test_csv.py	100.00% <0.00%> (ø)
... and 14 more

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[harrism]

rerun tests

[galipremsagar]

rerun tests