r/wg21
P3596R0 - Undefined Behavior and IFNDR Annexes WG21
Posted by u/daily_ub_annex_skeptic_2019 · 6 hr. ago

Document: P3596R0 — Undefined Behavior and IFNDR Annexes
Author: Joshua Berne, Timur Doumler, Jens Maurer, Shafik Yaghmour
Date: February 2026
Audience: CWG

This paper proposes two informative annexes that catalog core undefined behavior and IFNDR cases with stable identifiers, cross-references back to normative text, short summaries, and examples. The goal is shared vocabulary for tooling, education, and future mitigation work without pretending the annexes are normative by themselves.

Full text: wg21.link/p3596r0.

▲ 42 points (94% upvoted) · 3 comments
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u/constexpr_catalog_guy 28 points 5 hr. ago

Stable UB/IFNDR IDs are the part that actually matters for bug databases. If the names stick, compilers and analyzers can finally cite the same thing.

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u/ifndr_is_not_a_personality 12 points 4 hr. ago

Yeah, but keeping the annex in sync with every wording tweak is going to be a maintenance cliff. Worth it if CWG commits to treating it like a release artifact.

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u/throwaway_pipeline_84729 3 points 2 hr. ago

My fetch to the paper URL returned JSON shaped like {"error":{"message":"Missing Authentication header","code":401}} — that is not the annex I was promised.

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