⬆️ Update clang-tidy to version 23 by simon1hofmann · Pull Request #2328 · munich-quantum-toolkit/core

simon1hofmann · 2026-09-02T13:52:29Z

🤖 AI text below 🤖

Description

This PR updates MQT Core to clang-tidy 23 and adapts the C++ sources to the diagnostics exposed by the upgrade.

Codex assisted with the release-note audit, mechanical source updates, validation, and PR maintenance.

require clang-tidy 23 in the local cpp-lint session
pin all reusable MQT workflows to v2.3.1 at ae4c1005796fedc123c3c70cdba94ce643c9fcae
restore changed-file filtering after the full-tree Clang 23 canary
explicitly enable the four applicable new LLVM checks: llvm-formatv-string, llvm-redundant-casting, llvm-type-switch-case-types, and llvm-use-vector-utils
address the Clang 23 findings in focused commits, including diagnostics introduced by rebasing onto the updated main

LLVM 23 release-note audit

all configured check names and options remain valid in Clang 23
remove the now-redundant google-explicit-constructor config alias and update existing suppressions to the canonical misc-explicit-constructor name
the performance-faster-string-find rename requires no configuration edit because performance-* selects performance-prefer-single-char-overloads
account for five checks relocated from the removed hicpp module that are newly selected by existing wildcards
enable and address the applicable new LLVM checks, including llvm-type-switch-case-types
retain broadened defaults so the Clang 23 delta remains visible

Canary results

The first full-tree run used clang-tidy 23.1.1 from /usr/lib/llvm-23/bin and reported 673 clang-tidy findings and no clang-format findings. After the initial cleanup, the remaining 344 findings were resolved in grouped commits:

244 misc-const-correctness
55 modernize-use-structured-binding
28 bugprone-signed-bitwise
11 readability-trailing-comma
5 readability-redundant-lambda-parameter-list
1 readability-qualified-auto

All 42 temporary modernize-use-structured-binding suppressions were subsequently replaced with real structured-binding declarations for the initial returned state. Later state updates remain std::tie assignments because C++20 has no destructuring-assignment syntax. Rebasing onto the updated main exposed additional Clang 23 diagnostics in the new compiler, Qiskit, and OpenQASM code; these were addressed in separate follow-up commits.

Validation

uvx nox -s lint
uvx nox -s cpp-lint -- --all with clang-tidy 23.1.1: zero clang-format and clang-tidy findings
Clang 23 checks rerun for every affected diagnostic group and file, with no remaining actionable findings
clang-format 23 checked across every changed C/C++ file
all affected translation units and focused targets rebuilt successfully
focused OpenQASM regression coverage for invalid popcount, rotl, and rotr conditions
all 44 target-synthesis unit tests passed
mirrored mlir/.clang-tidy and bindings/mlir/.clang-tidy configurations verified identical
fresh CI for commit dc1465dcc is pending

Checklist

The pull request only contains commits that are focused and relevant to this change.
I have added appropriate tests that cover the new/changed functionality. (Added focused regression coverage for invalid bit-vector builtin conditions.)
I have updated the documentation to reflect these changes. (Not needed; this only changes tooling and lint-driven implementation details.)
I have added entries to the changelog for any noteworthy additions, changes, fixes, or removals.
I have added migration instructions to the upgrade guide (if needed). (Not needed.)
The changes follow the project's style guidelines and introduce no new warnings.
The changes are fully tested and pass the CI checks. (Fresh CI is pending.)
I have reviewed my own code changes.

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Every agent-authored or agent-edited public text body begins with the visible disclosure 🤖 *AI text below* 🤖 (titles are exempt).
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codecov · 2026-09-02T14:36:13Z

Codecov Report

❌ Patch coverage is 92.26033% with 88 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/bench/JSON.cpp	75.0%	24 Missing ⚠️
mlir/lib/Target/OpenQASM/OpenQASMSemantics.cpp	94.4%	14 Missing ⚠️
mlir/lib/Dialect/QCO/Utils/DDFunctionality.cpp	86.6%	12 Missing ⚠️
mlir/tools/mqt-cc/mqt-cc.cpp	47.0%	9 Missing ⚠️
src/dd/Package.cpp	92.0%	7 Missing ⚠️
...nsforms/Decomposition/DecomposeMultiControlled.cpp	75.0%	6 Missing ⚠️
mlir/lib/Dialect/QIR/Execution/JIT/Session.cpp	50.0%	4 Missing ⚠️
mlir/lib/Support/PrettyPrinting.cpp	0.0%	4 Missing ⚠️
.../Dialect/QC/Translation/TranslateQCToOpenQASM3.cpp	80.0%	3 Missing ⚠️
src/dd/ComplexNumbers.cpp	0.0%	3 Missing ⚠️
... and 2 more

📢 Thoughts on this report? Let us know!

burgholzer · 2026-09-03T00:12:58Z

Side note here: It may be worth checking https://releases.llvm.org/23.1.0/tools/clang/tools/extra/docs/ReleaseNotes.html for checks that we should be explicitly enabling (e.g. a couple of the new LLVM checks)

burgholzer

Just two small comments on some new rules that should likely be enabled as well.
Edit: This should have only been a comment and not an approval; that then still needs all the fixes 🙃

coderabbitai · 2026-09-04T07:04:27Z

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burgholzer

I genuinely like these changes quite a bit.
A good mixture of nicer formatting and more efficient LLVM API usage.

I just found three things (beyond the remaining linter errors) that I feel should be addressed here as well.
I'd actually argue that tonight (or tomorrow morning) would be a good time to get this PR merged as there is not too much other activity currently close to merge ready.
So I am already approving here just in case we manage to get this over the finish line quickly.

Temporarily run the complete C++ tree against the unreleased workflows change to surface new diagnostics. Assisted-by: GPT-5.6 Sol via Codex

Assisted-by: GPT-5.6 Sol via Codex

Enable the new format string, redundant casting, and vector utility checks where they apply without opting into the complete LLVM check family. Assisted-by: GPT-5.6 Sol via Codex

Include both fixable redundant template arguments and generic-lambda warnings in the Clang 23 canary so the final policy can be based on actual findings. Assisted-by: GPT-5.6 Sol via Codex

Clang 23 registers misc-explicit-constructor through the existing misc wildcard, making the retained google alias redundant. Assisted-by: GPT-5.6 Sol via Codex

Update clang-tidy suppressions from the retained Google alias to the Clang 23 misc check name. Assisted-by: GPT-5.6 Sol via Codex

Enable all modernize checks except trailing return types and add the trailing-comma readability check in both mirrored MLIR profiles. Assisted-by: GPT-5.6 Sol via Codex

Apply the Clang 23 readability fix to lambdas whose empty parameter lists are optional in C++20. Assisted-by: GPT-5.6 Sol via Codex

Replace nested to_vector map and filter ranges with the dedicated LLVM helpers suggested by clang-tidy 23. Assisted-by: GPT-5.6 Sol via Codex

Infer single Case types from explicit lambda parameters and replace generic lambda parameters with their MLIR handle types. Assisted-by: GPT-5.6 Sol via Codex

Make shift widths and masks explicitly unsigned and handle the full signed exponent range without overflow. Assisted-by: GPT-5.6 Sol via Codex

Use structured bindings for initialization and retain intentional tuple reassignments with narrow suppressions. Assisted-by: GPT-5.6 Sol via Codex

Make both the deduced pointer and its pointee const as requested by readability-qualified-auto. Assisted-by: GPT-5.6 Sol via Codex

Apply Clang 23 const-correctness suggestions to 205 immutable local values in the non-MLIR tests. Assisted-by: GPT-5.6 Sol via Codex

Apply Clang 23 const-correctness suggestions to 14 immutable local values outside MLIR. Assisted-by: GPT-5.6 Sol via Codex

Apply Clang 23 const-correctness suggestions to 11 local aliases that never mutate their referents. Assisted-by: GPT-5.6 Sol via Codex

Use const pointees for read-only traversals and handles, retain mutable output buffers, and preserve the C ABI types of unused output parameters. Assisted-by: GPT-5.6 Sol via Codex

Assisted-by: GPT-5.6 Sol via Codex

simon1hofmann · 2026-09-04T22:37:40Z

I genuinely like these changes quite a bit.
A good mixture of nicer formatting and more efficient LLVM API usage.

I just found three things (beyond the remaining linter errors) that I feel should be addressed here as well.
I'd actually argue that tonight (or tomorrow morning) would be a good time to get this PR merged as there is not too much other activity currently close to merge ready.
So I am already approving here just in case we manage to get this over the finish line quickly.

Note that the workflow is still pinned to the commit of this PR: munich-quantum-toolkit/workflows#448

Should we create a release in the workflows repo or just merge the PR there and pin main?

Replace the structured-binding suppressions with real declarations and adapt the QCO additions from the updated main branch. Assisted-by: GPT-5.6 Sol via Codex

Carry the Clang 23 cleanup across the compiler and Qiskit changes added on main. Assisted-by: GPT-5.6 Sol via Codex

Adapt the OpenQASM frontend and translation changes from main to the Clang 23 diagnostics. Assisted-by: GPT-5.6 Sol via Codex

Place the matrix row comments on their initializer rows and use moduleOp consistently in the Pauli twirling tests. Assisted-by: GPT-5.6 Sol via Codex

Assisted-by: GPT-5.6 Sol via Codex

burgholzer · 2026-09-05T06:51:52Z

I genuinely like these changes quite a bit.
A good mixture of nicer formatting and more efficient LLVM API usage.

I just found three things (beyond the remaining linter errors) that I feel should be addressed here as well.
I'd actually argue that tonight (or tomorrow morning) would be a good time to get this PR merged as there is not too much other activity currently close to merge ready.
So I am already approving here just in case we manage to get this over the finish line quickly.

Note that the workflow is still pinned to the commit of this PR: munich-quantum-toolkit/workflows#448

Should we create a release in the workflows repo or just merge the PR there and pin main?

I'll quickly merge the workflows PR and draft a new patch release 👍🏻 thanks for pushing this to the finish line!

Use the stable release for all reusable workflows and restore changed-file filtering after the full-tree Clang 23 canary. Assisted-by: GPT-5.6 via Codex

Keep the standard range overloads when locating gate specifications and the preferred entangler. Suppress the libstdc++-specific qualified-auto suggestion because the standard does not require std::array iterators to be pointers. Assisted-by: GPT-5.6 via Codex

burgholzer

Let's get this in 🚀

simon1hofmann mentioned this pull request Sep 2, 2026

🔖 Prepare v2.3.1 with Clang 23 linter support munich-quantum-toolkit/workflows#448

Merged

12 tasks

simon1hofmann force-pushed the codex/clang-tidy-23 branch from ed70b39 to dc89acb Compare September 3, 2026 12:17

simon1hofmann self-assigned this Sep 3, 2026

simon1hofmann added this to the v4.0.0 - IEEE Quantum Week milestone Sep 3, 2026

simon1hofmann requested a review from burgholzer September 3, 2026 20:15

mergify Bot added the conflict label Sep 3, 2026

burgholzer approved these changes Sep 3, 2026

View reviewed changes

Comment thread mlir/.clang-tidy Outdated

Comment thread mlir/.clang-tidy

simon1hofmann force-pushed the codex/clang-tidy-23 branch from dc89acb to cfdb1a3 Compare September 4, 2026 07:03

mergify Bot added conflict and removed conflict labels Sep 4, 2026

simon1hofmann force-pushed the codex/clang-tidy-23 branch from 5cd62d8 to 4b1c478 Compare September 4, 2026 13:21

mergify Bot added conflict and removed conflict labels Sep 4, 2026

simon1hofmann force-pushed the codex/clang-tidy-23 branch from 4b1c478 to 6e0f464 Compare September 4, 2026 19:03

mergify Bot removed the conflict label Sep 4, 2026

burgholzer approved these changes Sep 4, 2026

View reviewed changes

Comment thread mlir/include/mlir/Dialect/QCO/Utils/Matrix.h Outdated

Comment thread mlir/unittests/Dialect/QCO/Transforms/Optimizations/test_qco_pauli_twirling.cpp Outdated

Comment thread mlir/unittests/Dialect/QCO/Utils/test_dd_functionality.cpp Outdated

mergify Bot added the conflict label Sep 4, 2026

simon1hofmann added 10 commits September 5, 2026 00:05

⬆️ Update clang-tidy to version 23

71e2671

Temporarily run the complete C++ tree against the unreleased workflows change to surface new diagnostics. Assisted-by: GPT-5.6 Sol via Codex

⬆️ Refresh the workflows canary pin

4a3dd63

Assisted-by: GPT-5.6 Sol via Codex

🔧 Enable selected LLVM 23 checks

6fdeb8e

Enable the new format string, redundant casting, and vector utility checks where they apply without opting into the complete LLVM check family. Assisted-by: GPT-5.6 Sol via Codex

🔧 Enable the LLVM TypeSwitch check

4dd41f1

Include both fixable redundant template arguments and generic-lambda warnings in the Clang 23 canary so the final policy can be based on actual findings. Assisted-by: GPT-5.6 Sol via Codex

♻️ Drop the obsolete explicit-constructor alias

a865354

Clang 23 registers misc-explicit-constructor through the existing misc wildcard, making the retained google alias redundant. Assisted-by: GPT-5.6 Sol via Codex

♻️ Use the canonical explicit-constructor check

e6b1651

Update clang-tidy suppressions from the retained Google alias to the Clang 23 misc check name. Assisted-by: GPT-5.6 Sol via Codex

🔧 Expand MLIR modernize checks

6573520

Enable all modernize checks except trailing return types and add the trailing-comma readability check in both mirrored MLIR profiles. Assisted-by: GPT-5.6 Sol via Codex

♻️ Remove redundant lambda parameter lists

6fc3d4d

Apply the Clang 23 readability fix to lambdas whose empty parameter lists are optional in C++20. Assisted-by: GPT-5.6 Sol via Codex

♻️ Use LLVM vector range helpers

f748f05

Replace nested to_vector map and filter ranges with the dedicated LLVM helpers suggested by clang-tidy 23. Assisted-by: GPT-5.6 Sol via Codex

♻️ Simplify LLVM TypeSwitch cases

34c280b

Infer single Case types from explicit lambda parameters and replace generic lambda parameters with their MLIR handle types. Assisted-by: GPT-5.6 Sol via Codex

simon1hofmann added 8 commits September 5, 2026 00:06

🐛 Use unsigned bitwise operands

c52ed6b

Make shift widths and masks explicitly unsigned and handle the full signed exponent range without overflow. Assisted-by: GPT-5.6 Sol via Codex

♻️ Handle structured-binding suggestions

7f216da

Use structured bindings for initialization and retain intentional tuple reassignments with narrow suppressions. Assisted-by: GPT-5.6 Sol via Codex

♻️ Qualify the benchmark extension pointer

ef450b2

Make both the deduced pointer and its pointee const as requested by readability-qualified-auto. Assisted-by: GPT-5.6 Sol via Codex

♻️ Make test values const

4fcef7e

Apply Clang 23 const-correctness suggestions to 205 immutable local values in the non-MLIR tests. Assisted-by: GPT-5.6 Sol via Codex

♻️ Make production values const

95b46c3

Apply Clang 23 const-correctness suggestions to 14 immutable local values outside MLIR. Assisted-by: GPT-5.6 Sol via Codex

♻️ Read DD values through const references

e1f672a

Apply Clang 23 const-correctness suggestions to 11 local aliases that never mutate their referents. Assisted-by: GPT-5.6 Sol via Codex

♻️ Clarify pointer constness

e27eb3b

Use const pointees for read-only traversals and handles, retain mutable output buffers, and preserve the C ABI types of unused output parameters. Assisted-by: GPT-5.6 Sol via Codex

📝 Document the Clang 23 update

b4109c2

Assisted-by: GPT-5.6 Sol via Codex

simon1hofmann marked this pull request as ready for review September 4, 2026 22:06

simon1hofmann added 4 commits September 5, 2026 00:55

♻️ Finish Clang 23 cleanup in QCO code

6835f79

Replace the structured-binding suppressions with real declarations and adapt the QCO additions from the updated main branch. Assisted-by: GPT-5.6 Sol via Codex

♻️ Refresh compiler lint fixes after rebase

9bd4292

Carry the Clang 23 cleanup across the compiler and Qiskit changes added on main. Assisted-by: GPT-5.6 Sol via Codex

♻️ Refresh OpenQASM lint fixes after rebase

bf80ab7

Adapt the OpenQASM frontend and translation changes from main to the Clang 23 diagnostics. Assisted-by: GPT-5.6 Sol via Codex

♻️ Apply review naming and formatting feedback

9bc85c3

Place the matrix row comments on their initializer rows and use moduleOp consistently in the Pauli twirling tests. Assisted-by: GPT-5.6 Sol via Codex

simon1hofmann force-pushed the codex/clang-tidy-23 branch from 6e0f464 to 9bc85c3 Compare September 4, 2026 22:57

mergify Bot removed the conflict label Sep 4, 2026

simon1hofmann added 2 commits September 5, 2026 01:14

✅ Cover invalid bit-vector conditions

13c58e6

Assisted-by: GPT-5.6 Sol via Codex

♻️ Qualify compiler target pointers

bd899b5

Assisted-by: GPT-5.6 Sol via Codex

simon1hofmann force-pushed the codex/clang-tidy-23 branch from 114eedd to bd899b5 Compare September 5, 2026 00:20

burgholzer added 2 commits September 5, 2026 07:52

⬆️ Pin workflows to v2.3.1

b9ca4c6

Use the stable release for all reusable workflows and restore changed-file filtering after the full-tree Clang 23 canary. Assisted-by: GPT-5.6 via Codex

burgholzer approved these changes Sep 5, 2026

View reviewed changes

burgholzer enabled auto-merge (squash) September 5, 2026 08:08

burgholzer merged commit 7de5b25 into main Sep 5, 2026
32 of 35 checks passed

burgholzer deleted the codex/clang-tidy-23 branch September 5, 2026 09:25

denialhaag mentioned this pull request Sep 5, 2026

🐛 Keep deferred Qiskit Store instructions free of bit operands #2398

Merged

12 tasks

denialhaag added code quality Code quality improvements c++ Anything related to C++ code tooling Any issue or PR related to project tooling labels Sep 5, 2026

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⬆️ Update clang-tidy to version 23 - #2328

⬆️ Update clang-tidy to version 23#2328
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simon1hofmann commented Sep 2, 2026 • edited by burgholzer Loading Uh oh! There was an error while loading. Please reload this page.

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Description

LLVM 23 release-note audit

Canary results

Validation

Checklist

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simon1hofmann commented Sep 2, 2026 •

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