retoorandClaude Opus 4.8
79ae6f27da
Response to incident WA-2026-10-27 (the std::vector max_size() crash). Deep research archived under research/safe-cpp-practices (8 Tier 1, 37 Tier 2, 2 conclusions) on production-safe C++ that keeps development speed: OpenSSF compiler hardening, the C++ Core Guidelines bounds profile, integer-overflow practice, libFuzzer/sanitizer CI, the sanitizer overhead ladder, clang-tidy ratchets. The research prescribed an ASan+UBSan+_GLIBCXX_ASSERTIONS build of the parsers. Standing it up immediately caught a second, independent undefined-behavior bug that two manual reviews had missed: a protobuf varint loop that shifted by up to 70 bits (shift >= 64 is UB) on malformed input. Fixed and guarded by a deterministic test and the sanitizer net. - src/whatsapp/wa_proto.cpp: guard the wire-0 varint shift (the UB). - tests/whatsapp_test.cpp: add an overlong-varint hostile case. - tools/san-whatsapp.sh: the standing sanitizer net for detz::wa parsers. - WaClient frame capture: a frame that fails to decode/dispatch has its exact bytes recorded to <home>/whatsapp/last-error.log (bounded), so the still unreproduced live <iq> failure becomes a one-paste deterministic fix. Wired from the wizard and the whatsapp_send tool. - docs/cpp-safety.md: the project-wide playbook and design decisions (four layers: overflow-safe checked-reader parsing, cheap release hardening, the sanitizer test net, capture). docs/whatsapp.md section 13.6 records the follow-up and the honest open item. AGENTS.md makes it a standing rule; cap.md and mcp.md inherit it for their wire parsers. Verified: build, whatsapp_test (incl. hostile+fuzz), make lint, and tools/san-whatsapp.sh all green; research audit PASS. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
51 lines
2.2 KiB
Markdown
51 lines
2.2 KiB
Markdown
# C++ Core Guidelines: bounds safety, GSL, narrow_cast, not_null
|
|
|
|
## Metadata
|
|
|
|
| Field | Value |
|
|
|---|---|
|
|
| Institute | Molodetz Institute — Research & Retrieval Division |
|
|
| Subject | safe-cpp-practices |
|
|
| Document type | Source Dossier |
|
|
| Tier | 1 |
|
|
| Source title | C++ Core Guidelines: bounds safety, GSL, narrow_cast, not_null |
|
|
| Source URL | http://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines |
|
|
| Source publisher / author | Bjarne Stroustrup, Herb Sutter (editors), ISO C++ |
|
|
| Source type | standard |
|
|
| Source date (published) | Unknown — not stated (living document) |
|
|
| Date researched | 2026-10-27 |
|
|
| Researched by | tai (agent), model: Claude Opus 4.8, on behalf of retoor |
|
|
| Research method | web search synthesis |
|
|
| Confidence | High |
|
|
| Status | Active |
|
|
|
|
## Summary
|
|
|
|
The reference set of rules for modern C++. The bounds-safety profile treats range errors as a class to eliminate: pass span instead of pointer+length, and make narrowing conversions explicit and checked.
|
|
|
|
## Key findings
|
|
|
|
- Bounds profile: prefer `span` over raw pointer-plus-length parameters so a length cannot be passed wrong.
|
|
- `gsl::narrow<T>(x)` converts and throws `narrowing_error` if the value does not round-trip; `narrow_cast<T>` is an explicit, silent, lossy cast.
|
|
- ES.46: a negative double through `narrow<unsigned>` throws, while `narrow_cast` silently wraps, which is exactly the signed->size_t trap behind the WhatsApp crash.
|
|
- `gsl::not_null<T*>` documents and enforces that null is not a valid value for a pointer.
|
|
- The guidelines favor RAII and the rule of zero so resource bugs do not exist to be found.
|
|
|
|
## Pros / strengths
|
|
|
|
The canonical, broadly agreed rulebook; the span and narrow rules map directly onto wire parsing.
|
|
|
|
## Cons / limitations / caveats
|
|
|
|
Aspirational and large; full adoption is a multi-year ratchet. GSL is a dependency detz chose not to add (uses std::span/own checked reader instead).
|
|
|
|
## Relevance to tai
|
|
|
|
Names the exact anti-patterns detz hit (implicit narrowing, pointer+length) and the exact cures (explicit checked narrowing, span-style readers). detz applies the principle without the GSL dependency.
|
|
|
|
## Changelog
|
|
|
|
| Date | Change |
|
|
|---|---|
|
|
| 2026-10-27 | Initial dossier created (web search synthesis). |
|