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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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Sanitizer overhead and the debug/test/release maturity ladder

Metadata

Field	Value
Institute	Molodetz Institute — Research & Retrieval Division
Subject	safe-cpp-practices
Document type	Source Dossier
Tier	1
Source title	Sanitizer overhead and the debug/test/release maturity ladder
Source URL	https://microblink.com/be-wise-sanitize-keeping-your-c-code-free-from-bugs/
Source publisher / author	Microblink; Meeting C++ 2025 (Bloomberg); Sanitizers Handbook
Source type	blog post
Source date (published)	Unknown — not stated
Date researched	2026-10-27
Researched by	tai (agent), model: Claude Opus 4.8, on behalf of retoor
Research method	web search synthesis
Confidence	Medium
Status	Active

Summary

Sanitizers are a debug/test/fuzz tool, not a release one, because of their cost; cheap hardening flags stay on in release. Measured overheads: ASan ~2-3x, TSan ~5-15x, UBSan ~1.25x.

Key findings

ASan roughly 2-3x slowdown; TSan 5-15x; UBSan about 1.25x CPU and no memory overhead.
Sanitizers are too expensive for release; they belong in debug, test and fuzz builds.
Cheap hardening (fast hardening mode, stack-protector-strong) stays on in release.
A maturity ladder: local developer runs -> sanitizer CI -> nightly sanitizer suites -> fuzzing sanitizer jobs.
RAII and the rule of zero cost nothing at runtime and shrink the bug surface sanitizers must cover.

Pros / strengths

Gives the numbers needed to decide what gates release vs test; the ladder is a clear adoption plan.

Cons / limitations / caveats

Overhead figures vary by workload; blog/conference sourcing, not measured on detz.

Relevance to tai

Justifies detz's split: release gets the overflow-safe checks plus cheap libstdc++ assertions; the sanitizer net (ASan+UBSan) runs in the test suite, where it already caught a real UB varint bug.

Changelog

Date	Change
2026-10-27	Initial dossier created (web search synthesis).

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