Enforce east const via clang-format QualifierAlignment

[PointKernel]

Description

This PR updates the clang-format configuration to consistently enforce east const formatting across the codebase.

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.

[bdice]

Historically we did not enable this for some discovered reason, but I do not recall the details.

https://github.com/rapidsai/cudf/blob/2a52096f88e3cafb4c6f089c6ca801ff8c9aa810/cpp/doxygen/developer_guide/DEVELOPER_GUIDE.md?plain=1#L160-L163

[coderabbitai]

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📥 Commits

Reviewing files that changed from the base of the PR and between f0bcb42 and 967b44b.

📒 Files selected for processing (69)

• cpp/benchmarks/common/ndsh_data_generator/ndsh_data_generator.cpp
• cpp/benchmarks/common/ndsh_data_generator/random_column_generator.cu
• cpp/benchmarks/common/ndsh_data_generator/random_column_generator.hpp
• cpp/benchmarks/common/nvbench_utilities.cpp
• cpp/benchmarks/groupby/group_nunique.cpp
• cpp/benchmarks/io/cuio_common.cpp
• cpp/benchmarks/io/parquet/parquet_reader_filter.cpp
• cpp/examples/hybrid_scan_io/hybrid_scan_multifile_single_step.cpp
• cpp/examples/hybrid_scan_io/hybrid_scan_multifile_two_step.cpp
• cpp/include/cudf/strings/detail/gather.cuh
• cpp/include/cudf_test/nanoarrow_utils.hpp
• cpp/src/io/comp/brotli_dict.cpp
• cpp/src/io/comp/compression.cpp
• cpp/src/io/comp/debrotli.cu
• cpp/src/io/comp/decompression.cpp
• cpp/src/io/comp/gpuinflate.cu
• cpp/src/io/comp/snap.cu
• cpp/src/io/comp/unsnap.cu
• cpp/src/io/json/json_column.cu
• cpp/src/io/json/process_tokens.cu
• cpp/src/io/orc/stripe_data.cu
• cpp/src/io/orc/stripe_enc.cu
• cpp/src/io/orc/writer_impl.cu
• cpp/src/io/parquet/decode_fixed.cu
• cpp/src/io/parquet/page_decode.cuh
• cpp/src/io/parquet/page_string_decode.cu
• cpp/src/io/utilities/base64_utilities.cpp
• cpp/src/merge/merge.cu
• cpp/src/partitioning/partitioning.cu
• cpp/src/reductions/scan/ewm.cu
• cpp/src/rolling/jit/kernel.cu
• cpp/src/strings/copying/copy_range.cu
• cpp/src/utilities/cuda_memcpy.cu
• cpp/src/utilities/stream_pool.cpp
• cpp/src/utilities/time_utils.cuh
• cpp/tests/copying/copy_range_tests.cpp
• cpp/tests/copying/scatter_list_scalar_tests.cpp
• cpp/tests/copying/scatter_tests.cpp
• cpp/tests/dictionary/scatter_test.cpp
• cpp/tests/groupby/shift_tests.cpp
• cpp/tests/interop/from_arrow_device_test.cpp
• cpp/tests/interop/from_arrow_host_test.cpp
• cpp/tests/interop/from_arrow_test.cpp
• cpp/tests/interop/to_arrow_device_test.cpp
• cpp/tests/interop/to_arrow_host_test.cpp
• cpp/tests/io/csv_test.cpp
• cpp/tests/io/fst/fst_test.cu
• cpp/tests/io/json/json_test.cpp
• cpp/tests/io/json/json_tree.cpp
• cpp/tests/io/orc_test.cpp
• cpp/tests/io/parquet_common.cpp
• cpp/tests/io/parquet_misc_test.cpp
• cpp/tests/io/parquet_v2_test.cpp
• cpp/tests/iterator/optional_iterator_test_numeric.cu
• cpp/tests/iterator/pair_iterator_test_numeric.cu
• cpp/tests/iterator/value_iterator_test_transform.cu
• cpp/tests/join/join_tests.cpp
• cpp/tests/join/mixed_join_tests.cu
• cpp/tests/labeling/label_bins_tests.cpp
• cpp/tests/merge/merge_string_test.cpp
• cpp/tests/merge/merge_test.cpp
• cpp/tests/replace/replace_tests.cpp
• cpp/tests/rolling/grouped_rolling_test.cpp
• cpp/tests/rolling/rolling_test.cpp
• cpp/tests/round/round_tests.cpp
• cpp/tests/streams/copying_test.cpp
• cpp/tests/strings/array_tests.cpp
• cpp/tests/utilities/identify_stream_usage.cpp
• cpp/tests/wrappers/timestamps_test.cu

✅ Files skipped from review due to trivial changes (44)

• cpp/tests/strings/array_tests.cpp
• cpp/tests/iterator/pair_iterator_test_numeric.cu
• cpp/benchmarks/io/parquet/parquet_reader_filter.cpp
• cpp/examples/hybrid_scan_io/hybrid_scan_multifile_two_step.cpp
• cpp/src/io/utilities/base64_utilities.cpp
• cpp/tests/io/fst/fst_test.cu
• cpp/src/io/json/json_column.cu
• cpp/examples/hybrid_scan_io/hybrid_scan_multifile_single_step.cpp
• cpp/src/strings/copying/copy_range.cu
• cpp/src/io/parquet/decode_fixed.cu
• cpp/src/reductions/scan/ewm.cu
• cpp/tests/labeling/label_bins_tests.cpp
• cpp/tests/interop/from_arrow_device_test.cpp
• cpp/src/partitioning/partitioning.cu
• cpp/src/utilities/stream_pool.cpp
• cpp/src/utilities/cuda_memcpy.cu
• cpp/tests/interop/from_arrow_test.cpp
• cpp/tests/replace/replace_tests.cpp
• cpp/benchmarks/io/cuio_common.cpp
• cpp/tests/iterator/value_iterator_test_transform.cu
• cpp/tests/join/join_tests.cpp
• cpp/src/io/json/process_tokens.cu
• cpp/tests/io/parquet_v2_test.cpp
• cpp/tests/copying/copy_range_tests.cpp
• cpp/src/io/orc/writer_impl.cu
• cpp/tests/round/round_tests.cpp
• cpp/tests/io/json/json_tree.cpp
• cpp/src/io/orc/stripe_data.cu
• cpp/tests/interop/from_arrow_host_test.cpp
• cpp/tests/io/parquet_misc_test.cpp
• cpp/tests/join/mixed_join_tests.cu
• cpp/tests/io/parquet_common.cpp
• cpp/benchmarks/groupby/group_nunique.cpp
• cpp/src/io/comp/decompression.cpp
• cpp/tests/iterator/optional_iterator_test_numeric.cu
• cpp/tests/io/csv_test.cpp
• cpp/include/cudf/strings/detail/gather.cuh
• cpp/tests/merge/merge_string_test.cpp
• cpp/tests/interop/to_arrow_device_test.cpp
• cpp/tests/merge/merge_test.cpp
• cpp/tests/interop/to_arrow_host_test.cpp
• cpp/tests/rolling/rolling_test.cpp
• cpp/benchmarks/common/nvbench_utilities.cpp
• cpp/tests/io/json/json_test.cpp

🚧 Files skipped from review as they are similar to previous changes (24)

• cpp/tests/copying/scatter_list_scalar_tests.cpp
• cpp/src/io/parquet/page_decode.cuh
• cpp/src/utilities/time_utils.cuh
• cpp/include/cudf_test/nanoarrow_utils.hpp
• cpp/src/merge/merge.cu
• cpp/benchmarks/common/ndsh_data_generator/random_column_generator.hpp
• cpp/tests/io/orc_test.cpp
• cpp/src/io/comp/compression.cpp
• cpp/src/io/comp/snap.cu
• cpp/src/io/parquet/page_string_decode.cu
• cpp/src/io/orc/stripe_enc.cu
• cpp/src/rolling/jit/kernel.cu
• cpp/src/io/comp/debrotli.cu
• cpp/tests/wrappers/timestamps_test.cu
• cpp/tests/streams/copying_test.cpp
• cpp/benchmarks/common/ndsh_data_generator/random_column_generator.cu
• cpp/benchmarks/common/ndsh_data_generator/ndsh_data_generator.cpp
• cpp/src/io/comp/unsnap.cu
• cpp/tests/utilities/identify_stream_usage.cpp
• cpp/tests/groupby/shift_tests.cpp
• cpp/tests/dictionary/scatter_test.cpp
• cpp/src/io/comp/gpuinflate.cu
• cpp/tests/copying/scatter_tests.cpp
• cpp/tests/rolling/grouped_rolling_test.cpp

---

📝 Walkthrough

Summary by CodeRabbit

• Style
  • Standardized const/qualifier formatting across C++, CUDA, Java, and test code for consistency.
  • Updated clang-format behavior to align C++ type qualifiers in a uniform way.
• Tests
  • Adjusted benchmark and unit-test code to match the updated const/qualifier conventions.
• Chores
  • Refreshed SPDX/copyright header text across many source files.

Walkthrough

This PR adds QualifierAlignment: Right to .clang-format and applies equivalent const/volatile/CUDA qualifier-order reformatting across benchmark, core C++, test, and Java JNI native files. No functional logic, control flow, or public APIs are changed; a few host_span<const char* const> signatures are updated to host_span<char const* const>.

Changes

QualifierAlignment Right sweep

Layer / File(s)	Summary
Formatting policy switch .clang-format	Adds QualifierAlignment: Right to clang-format configuration.
Benchmarks and streaming surface updates cpp/benchmarks/..., cpp/examples/hybrid_scan_io/..., cpp/libcudf_streaming/benchmarks/..., cpp/libcudf_streaming/include/.../device_bloom_filter.hpp	Reorders const/qualifier placement in NDS-H data generator vocab spans, nvbench utilities, cuio benchmarks, parquet reader filter, hybrid scan examples, partition/shuffle benchmarks, and the bloom filter view return type.
Core C++ runtime updates cpp/librtcx/embed.hpp, cpp/src/hash/*, cpp/src/io/comp/*, cpp/src/io/orc/*, cpp/src/io/json/*, cpp/src/io/parquet/*, cpp/src/interop/to_arrow_host.cu, cpp/src/merge/merge.cu, cpp/src/partitioning/partitioning.cu, cpp/src/reductions/scan/ewm.cu, cpp/src/rolling/jit/kernel.cu, cpp/src/strings/copying/copy_range.cu, cpp/src/utilities/*, cpp/include/cudf/strings/detail/gather.cuh	Reorders const/volatile/__constant__ qualifiers in hashing constant tables, compression/decompression casts, ORC/Parquet/JSON decode paths, merge/partition/rolling kernel parameters, and utility helpers, plus a host_span element-type fix.
C++ test suite normalization cpp/tests/**, cpp/libcudf_streaming/tests/**, cpp/include/cudf_test/nanoarrow_utils.hpp	Reorders const qualifiers on local variables, loop variables, scalar reference_wrapper types, exception catch clauses, and lambda parameters across copying, dictionary, groupby, interop, IO, iterator, join, labeling, merge, reductions, replace, rolling, streams, and utility tests.
Java JNI native formatting updates java/src/main/native/src/AggregationJni.cpp, java/src/main/native/src/TableJni.cpp	Reorders const qualifier placement on local wrapper variables in JNI aggregation and table sort/order/merge entry points.

Estimated code review effort: 3 (Moderate) | ~30 minutes

Suggested labels: libcudf, Java, improvement, non-breaking, CMake

Suggested reviewers: bdice, davidwendt, vyasr, mhaseeb123, lamarrr

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 32.35% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately captures the main change: enforcing east const via clang-format qualifier alignment.
Description check	✅ Passed	The description is directly related to the changeset and matches the clang-format east const update.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

Warning

There were issues while running some tools. Please review the errors and either fix the tool's configuration or disable the tool if it's a critical failure.

🔧 ast-grep (0.44.0)

cpp/benchmarks/common/ndsh_data_generator/ndsh_data_generator.cpp

ast-grep exited with code unknown

cpp/benchmarks/common/ndsh_data_generator/random_column_generator.hpp

ast-grep exited with code unknown

cpp/benchmarks/common/nvbench_utilities.cpp

ast-grep exited with code unknown

• 17 others

---

_{Comment @coderabbitai help to get the list of available commands.}

[ttnghia]

Historically we did not enable this for some discovered reason, but I do not recall the details.

https://github.com/rapidsai/cudf/blob/2a52096f88e3cafb4c6f089c6ca801ff8c9aa810/cpp/doxygen/developer_guide/DEVELOPER_GUIDE.md?plain=1#L160-L163

Probably the new version is better now. We should enforce that and workaround if there issue with it.

[PointKernel]

The last similar attempt was quite early, e.g. #13493 where the bulk east-const conversion via clang-format's QualifierAlignment ran into issues on clang 14.

The upstream caveat is still there as of clang-format 20 but I reviewed the generated diff, and on our codebase it comes out clean: Pointer and volatile qualifiers reorder correctly because only the pointee qualifier moves (e.g. const char* const to char const* const, volatile int32_t* to int32_t volatile*), preserving the underlying types with no semantic swaps such as const T* to T* const. So I think we're safe to enforce it. If some future edge case ever trips it, // clang-format off/on coudl be the local escape hatch.

[vyasr]

IIRC @karthikeyann ended up using multiple tools to generate his old PRs, not just clang-format, because all of them tripped up in different ways. If everything is clean now that's great.

[karthikeyann]

clang-format missed a lot of places in previous attempt. Even after fixing with it, other tools found more instances.
clang-formats lack of complete semantic information.
https://releases.llvm.org/14.0.0/tools/clang/docs/ClangFormatStyleOptions.html#:~:text=COULD%20lead%20to%20incorrect%20code%20formatting

Warning
Setting QualifierAlignment to something other than Leave, COULD lead to incorrect code formatting due to incorrect decisions made due to clang-formats lack of complete semantic information. As such extra care should be taken to review code changes made by the use of this option.

[PointKernel]

It looks like the only cases clang-format missed were instances where const was used together with __constant__. We should really be using constexpr instead of const there, and once that's changed, the issue goes away. Fixed in f0bcb42

[vyasr]

All the changes look correct (as expected, it is also changing other qualifiers like volatile, which is fine). Let's merge it and see how it holds up for a while.

[PointKernel]

/merge

[karthikeyann]

Nice work 🎉
Please consider using other tools like https://github.com/biasmv/westerly etc and self created tools to do another run on entire repo. if these tools return nothing, then we can pretty much depend on clang-format.