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retoorandClaude Opus 4.8 79ae6f27da cpp-safety: safe-C++ playbook, fix a second UB, and a sanitizer net

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>

2026-10-27 19:03:32 +01:00

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C++ Core Guidelines: Bounds Safety

Metadata

Field	Value
Institute	Molodetz Institute — Research & Retrieval Division
Subject	safe-cpp-practices
Document type	Source Citation Card
Tier	2
Source title	C++ Core Guidelines: Bounds Safety
Source URL	https://www.modernescpp.com/index.php/c-core-guidelines-bounds-safety/
Source type	blog post
Date researched	2026-10-27
Researched by	tai (agent), model: Claude Opus 4.8, on behalf of retoor
Research method	Search aggregator result listing (not independently opened or quoted)
Confidence	Not independently verified
Status	Active

Why it's here

Bounds profile overview (claims span checks bounds, the weaker reading).

Changelog

Date	Change
2026-10-27	Logged as consulted-but-not-analyzed.

861 B Raw Blame History

C++ Core Guidelines: Bounds Safety

Metadata

Why it's here

Changelog

861 B

Raw Blame History