GH-53945: [C++] std::bit_width in ALP compression fails to compile with CRAN's macOS 11.3 SDK by thisisnic · Pull Request #53946 · apache/arrow

thisisnic · 2026-10-15T23:10:11Z

Rationale for this change

CI failures for CRAN macOS

What changes are included in this PR?

Use helper function which works on CRAN macOS in new code + refactor existing stuff

Are these changes tested?

Yup

Are there any user-facing changes?

Nope

Was AI used for this PR?

I generated the code with Claude Fable 5.1 and did adversarial reviews with Opus 5.5 and also asked some questions about why we were moving things into different files and if we had too many tests, resulting in trimming them down.

PR code and description written by:

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Reviewed before submission by:

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Not reviewed

GitHub Issue: [C++] std::bit_width in ALP compression fails to compile with CRAN's macOS 11.3 SDK #53945

thisisnic · 2026-10-15T23:10:40Z

@github-actions crossbow submit test-r-macos-as-cran

Copilot

🟢 Approval recommended

The focused refactor preserves existing calculations, reuses the established compatibility fallback, and adds targeted coverage with no identified blocking issues.

0 open findings

What changed in this PR

Fixes ALP compilation with CRAN’s macOS 11.3 SDK by centralizing the existing bit-width compatibility fallback.

Changes:

Adds bit_util::BitWidth and reuses it across Arrow and Parquet.
Tests unsigned boundary values and compile-time evaluation.

File	Description
cpp/src/parquet/encoder.cc	Uses the helper for delta bit widths.
cpp/src/parquet/chunker_internal.cc	Uses the helper for chunk masks.
cpp/src/arrow/util/rle_encoding_test.cc	Uses the helper in round-trip tests.
cpp/src/arrow/util/bit_util.h	Adds the compatibility helper and updates `Log2`.
cpp/src/arrow/util/bit_util_test.cc	Adds helper coverage.
cpp/src/arrow/util/alp/alp_compression.cc	Replaces incompatible bit-width calls.

🧠 Review effort: Balanced

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github-actions · 2026-10-15T23:15:41Z

Revision: 30307d4

Submitted crossbow builds: ursacomputing/crossbow @ actions-1e99b7a881

Task	Status
test-r-macos-as-cran

Copilot

🟢 Approval recommended

The focused refactor preserves existing calculations and fallback behavior, adds targeted coverage, and has no identified blocking issues.

0 open findings

🧠 Review effort: Balanced

thisisnic · 2026-10-16T08:17:07Z

@github-actions crossbow submit test-r-macos-as-cran

github-actions · 2026-10-16T08:22:39Z

Revision: 896343c

Submitted crossbow builds: ursacomputing/crossbow @ actions-bffabff8ca

Task	Status
test-r-macos-as-cran

Copilot

🔵 Needs a closer look

Compilation against the target macOS 11.3 SDK remains unverified, so the compatibility fallback needs confirmation.

0 open findings

🧠 Review effort: Balanced

thisisnic · 2026-10-30T10:55:06Z

@wgtmac - mind giving this a quick look over?

wgtmac · 2026-10-31T07:30:33Z


+// Returns ceil(log2(x)).
+static inline int Log2(uint64_t x) {
+  // DCHECK_GT(x, 0);


nit: remove this comment

edit: nothing here :)

Copilot

🔵 Needs a closer look

Human assessment is needed to evaluate an unpublished critical feature-test guard mismatch that can break compilation on newer Apple SDKs.

No open issues 🎉

_{Review effort: Balanced}

…w2-guard The BitWidth and HasSingleBit helpers added in apache#53946 replaced four of the five guard sites, so only the two guards in bit_util.h still need the new macro. Signed-off-by: 1fanwang <1fannnw@gmail.com>

thisisnic added 3 commits October 16, 2026 00:05

Split helper out better

1b35567

Add other helper usage

3f0fec9

Use helper in ALP compression

30307d4

Copilot AI balanced review requested due to automatic review settings October 15, 2026 23:10

thisisnic requested review from HuaHuaY, pitrou and wgtmac as code owners October 15, 2026 23:10

github-actions Bot added the awaiting committer review Awaiting committer review label Oct 15, 2026

github-actions Bot marked this pull request as draft October 15, 2026 23:13

github-actions Bot added Component: Parquet Component: C++ labels Oct 15, 2026

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thisisnic marked this pull request as ready for review October 15, 2026 23:16

Make it and int and don't cast int to int

c3b352e

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thisisnic marked this pull request as draft October 16, 2026 00:05

Add second helper function

896343c

thisisnic commented Oct 16, 2026

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Comment thread cpp/src/arrow/util/bit_util_test.cc Resolved

Trim tests

c4e05e0

github-actions Bot added awaiting changes Awaiting changes awaiting change review Awaiting change review and removed awaiting committer review Awaiting committer review awaiting changes Awaiting changes labels Oct 16, 2026

thisisnic marked this pull request as ready for review October 16, 2026 09:41

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github-actions Bot marked this pull request as draft October 16, 2026 09:47

thisisnic marked this pull request as ready for review October 18, 2026 17:27

thisisnic changed the title ~~53945: [C++] std::bit_width in ALP compression fails to compile with CRAN's macOS 11.3 SDK~~ GH-53945: [C++] std::bit_width in ALP compression fails to compile with CRAN's macOS 11.3 SDK Oct 20, 2026

thisisnic added this to the 27.0.0 milestone Oct 20, 2026

thisisnic added the Priority: Blocker Marks a blocker for the release label Oct 20, 2026

thisisnic requested a review from kou October 26, 2026 22:34

jonkeane mentioned this pull request Oct 27, 2026

GH-55267: [C++][R] Arrow 26.0.0 fails to build on CRAN macOS builders: bundled simdjson C++20 concepts don't compile with the macOS 11 SDK #55273

Merged

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wgtmac approved these changes Oct 31, 2026

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thisisnic commented Oct 31, 2026

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Comment thread cpp/src/arrow/util/bit_util.h Resolved

Apply suggestion from @thisisnic

70b63d3

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github-actions Bot added awaiting changes Awaiting changes and removed awaiting change review Awaiting change review labels Oct 31, 2026

thisisnic merged commit 340bf45 into apache:main Oct 31, 2026
58 of 60 checks passed

thisisnic removed the awaiting changes Awaiting changes label Oct 31, 2026

thisisnic mentioned this pull request Oct 31, 2026

[C++] std::bit_width in ALP compression fails to compile with CRAN's macOS 11.3 SDK #53945

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tadeja mentioned this pull request Oct 31, 2026

MINOR: [C++] Fix C++ Format #55353

Merged

2 tasks done

1fanwang mentioned this pull request Nov 1, 2026

GH-49841: [C++] Fix macOS 12.3 SDK build by using __cpp_lib_int_pow2 #50998

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GH-53945: [C++] std::bit_width in ALP compression fails to compile with CRAN's macOS 11.3 SDK - #53946

GH-53945: [C++] std::bit_width in ALP compression fails to compile with CRAN's macOS 11.3 SDK#53946
thisisnic merged 7 commits into
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thisisnic:GH-53945-cranalp

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thisisnic commented Oct 15, 2026 • edited by github-actions Bot Loading Uh oh! There was an error while loading. Please reload this page.

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Rationale for this change

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🟢 Approval recommended

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thisisnic commented Oct 15, 2026 •

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