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BUG: Avoid UB in safe_[add,sub,mul] helpers#31396

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ngoldbaum:fix-overflow-ub
May 7, 2026
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BUG: Avoid UB in safe_[add,sub,mul] helpers#31396
charris merged 1 commit into
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ngoldbaum:fix-overflow-ub

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Over in https://github.com/numpy/numpy/pull/31378/changes#r3190759945, I noticed that these helpers can trigger UB, since the result is always computed even if overflow might happen. A sufficiently aggressive compiler might optimize functionality away if it detects the undefined behavior.

Clang and gcc both have intrinsics to handle this, which we use if available. I had to add new probes for the add and sub builtin intrinsics. For the fallback cases, I added early returns to avoid triggering overflow.

I used Claude Opus 4.7 to help with this.

@charris charris added the 09 - Backport-Candidate PRs tagged should be backported label May 7, 2026
@charris charris merged commit 11b1baa into numpy:main May 7, 2026
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charris commented May 7, 2026

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Thanks Nathan. I marked this for backport as it seems straight forward.

@charris charris removed the 09 - Backport-Candidate PRs tagged should be backported label May 8, 2026
charris added a commit that referenced this pull request May 8, 2026
BUG: Avoid UB in safe_[add,sub,mul] helpers (#31396)
736-c41-2c1-e464fc974 added a commit to Swiss-Armed-Forces/Loom that referenced this pull request Jun 29, 2026
This MR contains the following updates:

| Package | Type | Update | Change | OpenSSF |
|---|---|---|---|---|
| [debugpy](https://aka.ms/debugpy) ([source](https://github.com/microsoft/debugpy)) | dev | patch | `1.8.20` → `1.8.21` | [![OpenSSF Scorecard](https://api.securityscorecards.dev/projects/github.com/microsoft/debugpy/badge)](https://securityscorecards.dev/viewer/?uri=github.com/microsoft/debugpy) |
| [numpy](https://github.com/numpy/numpy) ([changelog](https://numpy.org/doc/stable/release)) | dependencies | patch | `2.4.4` → `2.4.6` | [![OpenSSF Scorecard](https://api.securityscorecards.dev/projects/github.com/numpy/numpy/badge)](https://securityscorecards.dev/viewer/?uri=github.com/numpy/numpy) |
| [pydantic-settings](https://github.com/pydantic/pydantic-settings) ([changelog](https://github.com/pydantic/pydantic-settings/releases)) | dependencies | patch | `2.14.0` → `2.14.2` | [![OpenSSF Scorecard](https://api.securityscorecards.dev/projects/github.com/pydantic/pydantic-settings/badge)](https://securityscorecards.dev/viewer/?uri=github.com/pydantic/pydantic-settings) |
| [python-multipart](https://github.com/Kludex/python-multipart) ([changelog](https://github.com/Kludex/python-multipart/blob/master/CHANGELOG.md)) | dependencies | patch | `^0.0.22` → `^0.0.32` | [![OpenSSF Scorecard](https://api.securityscorecards.dev/projects/github.com/Kludex/python-multipart/badge)](https://securityscorecards.dev/viewer/?uri=github.com/Kludex/python-multipart) |
| [types-requests](https://github.com/python/typeshed) ([changelog](https://github.com/typeshed-internal/stub_uploader/blob/main/data/changelogs/requests.md)) | dependencies | patch | `2.32.0.20240523` → `2.32.4.20260324` | [![OpenSSF Scorecard](https://api.securityscorecards.dev/projects/github.com/python/typeshed/badge)](https://securityscorecards.dev/viewer/?uri=github.com/python/typeshed) |

---

### Release Notes

<details>
<summary>microsoft/debugpy (debugpy)</summary>

### [`v1.8.21`](https://github.com/microsoft/debugpy/releases/tag/v1.8.21): debugpy v1.8.21

[Compare Source](microsoft/debugpy@v1.8.20...v1.8.21)

Fixes for:

- Return evaluate result in DAP response body instead of writing to stdout: [#&#8203;2027](microsoft/debugpy#2027)
- Prevent invalid `scopes` request from crashing debug session: [#&#8203;2026](microsoft/debugpy#2026)
- Skip uninitialized `__slots__` in variable resolver: [#&#8203;2024](microsoft/debugpy#2024)
- Handle `-c` arguments that are `bytes` instead of `str`: [#&#8203;2021](microsoft/debugpy#2021)
- Fix evaluation of variables from chained exception frames: [#&#8203;2018](microsoft/debugpy#2018)
- `ContinueRequest` with a specific `threadId` no longer resumes all threads (in-process adapter): [#&#8203;2012](microsoft/debugpy#2012)
- Avoid strong reference to exceptions during unwind: [#&#8203;2008](microsoft/debugpy#2008)
- Show error message on evaluate failures in the hover context: [#&#8203;2006](microsoft/debugpy#2006)
- Display `dlerror` output when `dlopen` fails: [#&#8203;2000](microsoft/debugpy#2000)
- Replace removed `pkgutil.get_loader` with `importlib.util.find_spec` in `get_fullname`: [#&#8203;1998](microsoft/debugpy#1998)

Enhancements:

- Add option to ignore all system exit codes: [#&#8203;2017](microsoft/debugpy#2017)
- Pull changes from pydevd up to March 2026: [#&#8203;2010](microsoft/debugpy#2010)

Infrastructure work:

- Suppress Flawfinder false positives on Cython memcpy / read-loop iterators (TSA [#&#8203;2816216](https://github.com/microsoft/debugpy/issues/2816216), [#&#8203;2816217](https://github.com/microsoft/debugpy/issues/2816217), [#&#8203;2816218](https://github.com/microsoft/debugpy/issues/2816218), [#&#8203;2816219](https://github.com/microsoft/debugpy/issues/2816219), [#&#8203;2816220](https://github.com/microsoft/debugpy/issues/2816220)): [#&#8203;2028](microsoft/debugpy#2028), [#&#8203;2029](microsoft/debugpy#2029), [#&#8203;2030](microsoft/debugpy#2030), [#&#8203;2031](microsoft/debugpy#2031), [#&#8203;2032](microsoft/debugpy#2032)

Thanks to [@&#8203;maxbachmann](https://github.com/maxbachmann), [@&#8203;mfussenegger](https://github.com/mfussenegger), and [@&#8203;sambrightman](https://github.com/sambrightman) for the commits.

</details>

<details>
<summary>numpy/numpy (numpy)</summary>

### [`v2.4.6`](https://github.com/numpy/numpy/releases/tag/v2.4.6): (May 18, 2026)

[Compare Source](numpy/numpy@v2.4.5...v2.4.6)

### NumPy 2.4.6 Release Notes

NumPy 2.4.6 is a quick release that fixes a regression discovered in the 2.4.5
release.

This release supports Python versions 3.11-3.14

#### Contributors

A total of 4 people contributed to this release. People with a "+" by their
names contributed a patch for the first time.

- !EarlMilktea
- Charles Harris
- Sebastian Berg
- Warren Weckesser

#### Pull requests merged

A total of 4 pull requests were merged for this release.

- [#&#8203;31444](numpy/numpy#31444): MAINT: Prepare 2.4.x for further development
- [#&#8203;31453](numpy/numpy#31453): BUG: Fix regression in `arr.conj()`
- [#&#8203;31459](numpy/numpy#31459): BUG: `np.linalg.svd(..., hermitian=True)` returns non-unitary...
- [#&#8203;31460](numpy/numpy#31460): BUG: Don't call INCREF/DECREF on descr in NpyStringAcquireAllocator...

### [`v2.4.5`](https://github.com/numpy/numpy/releases/tag/v2.4.5): (May 15, 2026)

[Compare Source](numpy/numpy@v2.4.4...v2.4.5)

### NumPy 2.4.5 Release Notes

NumPy 2.4.5 is a patch release that fixes bugs discovered after the 2.4.4
release, has some typing improvements, and maintains infrastructure.

This release supports Python versions 3.11-3.14

#### Contributors

A total of 17 people contributed to this release. People with a "+" by their
names contributed a patch for the first time.

- Aleksei Nikiforov
- Anarion Zuo +
- Ankit Ahlawat
- Breno Favaretto +
- Charles Harris
- Igor Krivenko +
- Ijtihed Kilani +
- Joren Hammudoglu
- Maarten Baert +
- Matti Picus
- Nathan Goldbaum
- Praneeth Kodumagulla +
- Ralf Gommers
- RoomWithOutRoof +
- Sebastian Berg
- Warren Weckesser
- div +

#### Pull requests merged

A total of 28 pull requests were merged for this release.

- [#&#8203;31093](numpy/numpy#31093): MAINT: Prepare 2.4.x for further development
- [#&#8203;31182](numpy/numpy#31182): TYP: fix `np.shape` assignability issue for python lists ([#&#8203;31171](numpy/numpy#31171))
- [#&#8203;31197](numpy/numpy#31197): ENH: Return rank 0 for empty matrices in matrix\_rank ([#&#8203;30422](numpy/numpy#30422))
- [#&#8203;31198](numpy/numpy#31198): CI/BUG: add native jobs for s390x, fix bug in `pack_inner`...
- [#&#8203;31199](numpy/numpy#31199): BUG: f2py map complex\_long\_double to NPY\_CLONGDOUBLE
- [#&#8203;31205](numpy/numpy#31205): MAINT: f2py: Stop setting re.\_MAXCACHE to 50.
- [#&#8203;31206](numpy/numpy#31206): BUG: fix heap buffer overflow in timedelta to string casts
- [#&#8203;31207](numpy/numpy#31207): MAINT: Rename ppc64le and s390x workflow ([#&#8203;31121](numpy/numpy#31121))
- [#&#8203;31208](numpy/numpy#31208): BUG: Fix matvec/vecmat in-place aliasing (out=input produces...
- [#&#8203;31209](numpy/numpy#31209): TYP: `tile`: accept numpy scalars and arrays as second argument...
- [#&#8203;31211](numpy/numpy#31211): DEP: Undo deprecation for np.dtype() signature used by old pickles...
- [#&#8203;31212](numpy/numpy#31212): REV: Manual revert of float16 svml use ([#&#8203;31178](numpy/numpy#31178))
- [#&#8203;31222](numpy/numpy#31222): TYP: `ix_` fix for boolean and non-1d input ([#&#8203;31218](numpy/numpy#31218))
- [#&#8203;31329](numpy/numpy#31329): BUG: incorrect temp elision for new-style (NEP 43) user-defined...
- [#&#8203;31330](numpy/numpy#31330): TYP: fix sliding\_window\_view axis parameter typing
- [#&#8203;31335](numpy/numpy#31335): BUG: Prevent deadlock due to downstream importing NumPy in dlopen...
- [#&#8203;31336](numpy/numpy#31336): BUG: Fix segfault in nditer.multi\_index when \_\_getitem\_\_ raises...
- [#&#8203;31338](numpy/numpy#31338): TYP: Fix ruff lint error
- [#&#8203;31357](numpy/numpy#31357): BUG: fix memory leak in np.zeros when fill-zero loop raises ([#&#8203;31320](numpy/numpy#31320))
- [#&#8203;31358](numpy/numpy#31358): BUG: np.einsum() fails with a 0-dimensional out argument and...
- [#&#8203;31379](numpy/numpy#31379): BUG: Fix signed overflow issue in npy\_gcd for INT\_MIN on s390x...
- [#&#8203;31383](numpy/numpy#31383): CI: remove Cirrus CI FreeBSD job ([#&#8203;31380](numpy/numpy#31380))
- [#&#8203;31390](numpy/numpy#31390): BUILD: newer MKL uses so.3
- [#&#8203;31391](numpy/numpy#31391): BLD/MAINT: improve support for Intel LLVM compilers
- [#&#8203;31401](numpy/numpy#31401): BUG: Avoid UB in [safe]()\[add,sub,mul] helpers ([#&#8203;31396](numpy/numpy#31396))
- [#&#8203;31402](numpy/numpy#31402): BUG: exclude \_\_pycache\_\_ directories from wheels ([#&#8203;31397](numpy/numpy#31397))
- [#&#8203;31404](numpy/numpy#31404): TYP: `_NestedSequence` type parameter default to work around...
- [#&#8203;31426](numpy/numpy#31426): TYP: Fix `DTypeLike` runtime type-checker support ([#&#8203;31425](numpy/numpy#31425))

</details>

<details>
<summary>pydantic/pydantic-settings (pydantic-settings)</summary>

### [`v2.14.2`](https://github.com/pydantic/pydantic-settings/releases/tag/v2.14.2)

[Compare Source](pydantic/pydantic-settings@v2.14.1...v2.14.2)

#### What's Changed

This is a security patch release.

- Prevent `NestedSecretsSettingsSource` from following symlinks outside `secrets_dir` by [@&#8203;hramezani](https://github.com/hramezani) in [#&#8203;889](pydantic/pydantic-settings#889)
- Prepare release 2.14.2 by [@&#8203;hramezani](https://github.com/hramezani) in [#&#8203;890](pydantic/pydantic-settings#890)

##### Security

Fixes [GHSA-4xgf-cpjx-pc3j](GHSA-4xgf-cpjx-pc3j): `NestedSecretsSettingsSource` with `secrets_nested_subdir=True` could follow a symbolic link inside `secrets_dir` pointing outside it, reading out-of-tree files into settings values and bypassing the `secrets_dir_max_size` cap. Affected versions: `>= 2.12.0, < 2.14.2`.

**Full Changelog**: <pydantic/pydantic-settings@v2.14.1...v2.14.2>

### [`v2.14.1`](https://github.com/pydantic/pydantic-settings/releases/tag/v2.14.1)

[Compare Source](pydantic/pydantic-settings@v2.14.0...v2.14.1)

#### What's Changed

- Bump the python-packages group with 4 updates by [@&#8203;dependabot](https://github.com/dependabot)\[bot] in [#&#8203;850](pydantic/pydantic-settings#850)
- Bump the python-packages group with 5 updates by [@&#8203;dependabot](https://github.com/dependabot)\[bot] in [#&#8203;854](pydantic/pydantic-settings#854)
- Bump the github-actions group with 3 updates by [@&#8203;dependabot](https://github.com/dependabot)\[bot] in [#&#8203;853](pydantic/pydantic-settings#853)
- Bump the python-packages group with 2 updates by [@&#8203;dependabot](https://github.com/dependabot)\[bot] in [#&#8203;856](pydantic/pydantic-settings#856)
- Fix field named `cls` conflicting with classmethod parameter by [@&#8203;hramezani](https://github.com/hramezani) in [#&#8203;858](pydantic/pydantic-settings#858)
- Prepare release 2.14.1 by [@&#8203;hramezani](https://github.com/hramezani) in [#&#8203;859](pydantic/pydantic-settings#859)

**Full Changelog**: <pydantic/pydantic-settings@v2.14.0...v2.14.1>

</details>

<details>
<summary>Kludex/python-multipart (python-multipart)</summary>

### [`v0.0.32`](https://github.com/Kludex/python-multipart/blob/HEAD/CHANGELOG.md#0032-2026-06-04)

[Compare Source](Kludex/python-multipart@0.0.31...0.0.32)

- Speed up partial-boundary scanning for CR/LF-dense part data [#&#8203;300](Kludex/python-multipart#300).

### [`v0.0.31`](https://github.com/Kludex/python-multipart/blob/HEAD/CHANGELOG.md#0031-2026-06-04)

[Compare Source](Kludex/python-multipart@0.0.30...0.0.31)

- Speed up multipart header parsing and callback dispatch [#&#8203;295](Kludex/python-multipart#295).
- Bound header field name size before validating [#&#8203;296](Kludex/python-multipart#296).
- Validate `Content-Length` is non-negative in `parse_form` [#&#8203;297](Kludex/python-multipart#297).

### [`v0.0.30`](https://github.com/Kludex/python-multipart/blob/HEAD/CHANGELOG.md#0030-2026-05-31)

[Compare Source](Kludex/python-multipart@0.0.29...0.0.30)

- Parse `application/x-www-form-urlencoded` bodies per the WHATWG URL standard, treating only `&` as a field separator [#&#8203;290](Kludex/python-multipart#290).
- Ignore RFC 2231/5987 extended parameters (`name*`, `filename*`) in `parse_options_header`, keeping the plain parameter authoritative per [RFC 7578 §4.2](https://datatracker.ietf.org/doc/html/rfc7578#section-4.2) [#&#8203;291](Kludex/python-multipart#291).

### [`v0.0.29`](https://github.com/Kludex/python-multipart/blob/HEAD/CHANGELOG.md#0029-2026-05-17)

[Compare Source](Kludex/python-multipart@0.0.28...0.0.29)

- Handle malformed RFC 2231 continuations in `parse_options_header` [#&#8203;270](Kludex/python-multipart#270).

### [`v0.0.28`](https://github.com/Kludex/python-multipart/blob/HEAD/CHANGELOG.md#0028-2026-05-10)

[Compare Source](Kludex/python-multipart@0.0.27...0.0.28)

- Speed up partial-boundary tail scan via `bytes.find` [#&#8203;281](Kludex/python-multipart#281).
- Cap multipart boundary length at 256 bytes [#&#8203;282](Kludex/python-multipart#282).

### [`v0.0.27`](https://github.com/Kludex/python-multipart/blob/HEAD/CHANGELOG.md#0027-2026-04-27)

[Compare Source](Kludex/python-multipart@0.0.26...0.0.27)

- Add multipart header limits [#&#8203;267](Kludex/python-multipart#267).
- Pass parse offsets via constructors [#&#8203;268](Kludex/python-multipart#268).

### [`v0.0.26`](https://github.com/Kludex/python-multipart/blob/HEAD/CHANGELOG.md#0026-2026-04-10)

[Compare Source](Kludex/python-multipart@0.0.25...0.0.26)

- Skip preamble before the first multipart boundary more efficiently [#&#8203;262](Kludex/python-multipart#262).
- Silently discard epilogue data after the closing multipart boundary [#&#8203;259](Kludex/python-multipart#259).

### [`v0.0.25`](https://github.com/Kludex/python-multipart/blob/HEAD/CHANGELOG.md#0025-2026-04-10)

[Compare Source](Kludex/python-multipart@0.0.24...0.0.25)

- Add MIME content type info to `File` [#&#8203;143](Kludex/python-multipart#143).
- Handle CTE values case-insensitively [#&#8203;258](Kludex/python-multipart#258).
- Remove custom `FormParser` classes [#&#8203;257](Kludex/python-multipart#257).
- Add `UPLOAD_DELETE_TMP` to `FormParser` config [#&#8203;254](Kludex/python-multipart#254).
- Emit `field_end` for trailing bare field names on finalize [#&#8203;230](Kludex/python-multipart#230).
- Handle multipart headers case-insensitively [#&#8203;252](Kludex/python-multipart#252).
- Apply Apache-2.0 properly [#&#8203;247](Kludex/python-multipart#247).

### [`v0.0.24`](https://github.com/Kludex/python-multipart/blob/HEAD/CHANGELOG.md#0024-2026-04-05)

[Compare Source](Kludex/python-multipart@0.0.23...0.0.24)

- Validate `chunk_size` in `parse_form()` [#&#8203;244](Kludex/python-multipart#244).

### [`v0.0.23`](https://github.com/Kludex/python-multipart/blob/HEAD/CHANGELOG.md#0023-2026-04-05)

[Compare Source](Kludex/python-multipart@0.0.22...0.0.23)

- Remove unused `trust_x_headers` parameter and `X-File-Name` fallback [#&#8203;196](Kludex/python-multipart#196).
- Return processed length from `QuerystringParser._internal_write` [#&#8203;229](Kludex/python-multipart#229).
- Cleanup metadata dunders from `__init__.py` [#&#8203;227](Kludex/python-multipart#227).

</details>

---

 - [ ] <!-- rebase-check -->If you want to rebase/retry this MR, check this box

---

This MR has been generated by [Mend Renovate](https://github.com/renovatebot/renovate).
<!--renovate-debug:eyJjcmVhdGVkSW5WZXIiOiI0My4xMTAuMTYiLCJ1cGRhdGVkSW5WZXIiOiI0My4yNDYuMSIsInRhcmdldEJyYW5jaCI6Im1haW4iLCJsYWJlbHMiOlsiZGVwZW5kZW5jaWVzIiwicmVub3ZhdGUiXX0=-->

See merge request swiss-armed-forces/cyber-command/cea/loom!460

Co-authored-by: Loom MR Pipeline Trigger <group_103951964_bot_9504bb8dead6d4e406ad817a607f24be@noreply.gitlab.com>
Co-authored-by: shrewd-laidback palace <shrewd-laidback-palace-736-c41-2c1-e464fc974@swiss-armed-forces-open-source.ch>
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