Sandbox::https://github.com/RustPython/RustPython/pull/8959

youknowdot · 2026-10-04T13:41:56Z

A sparse memo entry changes the index chosen by MEMOIZE: after BINPUT 7, the next implicit memo index must be 1, not 8. The vector length currently makes a subsequent BINGET 1 fail.

Store populated memo entries in a map and choose the implicit index from their count. Preserve ascending memo.copy() order, reserve storage fallibly, and release displaced values after memo guards end. Add one bounded, unique sparse/MEMOIZE regression after comparing coverage with the canonical pickle tests.

This is extracted from #8954 onto current main's unchanged Python 3.14 target. It changes no pickle protocol version or 3.15 language behavior. The mega PR retains the implementation until this independent change is merged.

Fresh standalone validation on cccc67bdf9929948976933c3b9a678a346e8bf06:

Rust workspace: 1,345 passed /18 ignored; separate C-API: 116 passed /4 ignored
Both Clippy gates pass without warnings; release startup confirms Python 3.14 and marshal/pickle version 5
test_pickle: 1,008 run, 73 skipped, 5 retained expected failures; test_pickletools: 190 run, 14 skipped, 1 retained expected failure. Both complete successfully
New sparse regression passes native RustPython and exact CPython 3.14.7
Five bounded native contract groups and four memo-finalizer reentry operations pass, including copying the memo during clear, replacement, overwrite and reinitialization
Full snippets: 470 passed /12 environment failures. Native 235/4, CPython 3.14.7 reference 235/4, host harness 0/4. The failing multiprocessing/ownership cases have the same AF_UNIX/UID-map restrictions on both interpreters; no source skips or assertions were weakened
Normal configured commit hooks pass

CPython 3.14.7 agrees on sparse opcode/MEMOIZE and protocol roundtrips. Its explicit sparse dictionary-assignment/copy cases omit entries; those two cases are checked as preservation of existing RustPython behavior, rather than claimed reference parity. This patch does not establish general unpickler GC or recursive-load safety.

AI assistance: prepared, reviewed and tested with Codex at the user's direction. Exact model metadata is unavailable; the commit records Assisted-by: Codex:model-version-unavailable.

Summary by CodeRabbit

Bug Fixes
- Fixed pickle loading for streams with gaps in memo indices, preserving shared object references and correctly assigning subsequent memo entries.

A sparse BINPUT followed by MEMOIZE must use the number of occupied memo entries, not the largest index plus one. Store populated entries in a map, preserve ascending memo copies, reserve fallibly, and release displaced references after memo guards end. Keep existing memo assignment/proxy behavior and add one bounded regression for sparse BINPUT, MEMOIZE identity and copy order. No protocol version, GC traversal or unrelated pickle input changes are included. Extracted from the Python 3.15 migration onto the unchanged 3.14 target. Assisted-by: Codex:model-version-unavailable

coderabbitai · 2026-10-04T13:42:05Z

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📒 Files selected for processing (1)

extra_tests/snippets/stdlib_pickle.py

💤 Files with no reviewable changes (1)

extra_tests/snippets/stdlib_pickle.py

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📝 Walkthrough

Walkthrough

Unpickler memo storage now uses a sparse map. Memo opcodes and proxy operations use the updated representation, and a regression test checks memo holes, keys, and object identity.

Changes

Pickle memo handling

Layer / File(s)	Summary
Sparse memo representation and helpers `crates/stdlib/src/pickle.rs`	The unpickler memo uses a `HashMap` with fallible copy and insertion helpers. Constructors initialize an empty map.
Memo proxy and replacement lifecycle `crates/stdlib/src/pickle.rs`	Proxy copies return entries in index order. Dictionary assignment validates nonnegative integer keys and reports allocation failures as `MemoryError`. Clearing, reinitializing, and replacing the memo take old contents out of the lock before dropping them.
Memo opcode writes `crates/stdlib/src/pickle.rs`, `extra_tests/snippets/stdlib_pickle.py`	Memo write opcodes use the updated insertion path. `MEMOIZE` selects an index from the number of memo entries. The regression test checks sparse keys and shared object identity.

Priority: ⬇️ Low

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Bug fix

Suggested reviewers: youknowone

Merge Risk: ⚪ Minimal · up to f4c7e

No actionable issue is established for the selected change; it is mergeable after normal checks.

Security Architecture Review

Security architecture risk: 🔵 Low · up to cccc6

The change keeps memo ownership within each unpickler, avoids allocation for sparse-index gaps, and releases displaced objects outside memo locks. No introduced security vulnerability was identified. Residual uncertainty concerns broader finalizer behavior and recovery after failed loads, rather than a new privilege or service boundary.

Retained concerns
No architecture-level concerns identified.

Security review details

Security Blast Radius

inferred — The directly changed state is one unpickler's memo and its referenced Python objects within the interpreter process. Sparse storage does not establish an isolation boundary: broader object-resolution authority remains dependent on the existing unpickling hooks and caller context.

Security Findings and Attack Paths

inferred — The inspected memo changes do not introduce a new authority-bearing sink. Pickle-controlled indices select existing memo references or store the stack value, while absent entries fail. Existing class-resolution and persistent-load hooks remain outside the changed memo implementation.

Trust Boundaries and Controls

observed — The public memo setter rejects deletion, unsupported value types, noninteger keys, and negative representable indices. It builds a separate replacement map before swapping the owner's live memo. Memoize count selection and insertion share one write guard, avoiding a count-to-insert race.

Resilience and Maintainability Implications

observed — A large explicit memo index now reserves only an entry rather than vector gaps. Copy and replacement reserve according to populated-entry counts and map reservation failures to MemoryError. This reduces sparse-index allocation amplification, but does not bound total entries supplied by a pickle or dictionary.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 35.71% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 14 functions across 3 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly states the main change: MEMOIZE indexes use the count of populated unpickler memo entries.
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.

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chatgpt-codex-connector · 2026-10-04T13:46:17Z

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codspeed · 2026-10-04T15:03:27Z

Merging this PR will not alter performance

✅ 62 untouched benchmarks
⏩ 4 skipped benchmarks¹

_{Comparing youknowdot:python314-sparse-memo (cccc67b) with main (f39b054)}

4 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

youknowone · 2026-10-04T15:20:55Z

stdlib_pickle.py
do not add new test file without good reason

Renamed it to extra_tests/snippets/stdlib_pickle.py in f4c7ea16. There was no existing stdlib_pickle.py on this branch, so this is a 100% rename: the regression's contents and assertions are unchanged. Test discovery and execution under the new name pass with both RustPython and CPython 3.14.7.

Use the module-level snippet name requested in review without changing the regression assertions. Assisted-by: Codex:model-version-unavailable

youknowone marked this pull request as ready for review October 4, 2026 13:46

youknowone requested changes Oct 4, 2026

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youknowdot mentioned this pull request Oct 4, 2026

Prepare Python 3.15 with rc3 libraries and native prerequisites #8954

Draft

Move sparse memo regression to standard pickle snippet

f4c7ea1

Use the module-level snippet name requested in review without changing the regression assertions. Assisted-by: Codex:model-version-unavailable

youknowone approved these changes Oct 5, 2026

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youknowone merged commit 5a61850 into RustPython:main Oct 5, 2026
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Use populated entries for unpickler MEMOIZE indexes - #8959

Use populated entries for unpickler MEMOIZE indexes#8959
youknowone merged 2 commits into
RustPython:mainfrom
youknowdot:python314-sparse-memo

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Merging this PR will not alter performance

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