Keynote: Contracts, Testing & the Pursuit of Well Defined Behaviour

on YouTube ↗01h 34m

" summary

Shows that language-level preconditions and a small Contracts MVP (pre/post/assert) aim for C++26, with an implementation model that supports enforce/observe/ignore semantics and a replaceable violation handler (prints diagnostics or throws for test harnesses). Documents how UB (off-by-one, signed overflow) gets optimized away, how assume (available in C++23/GCC13) yields faster code, and why testing contracts uses exceptions not noexcept and why death tests or fork/spawn hacks are impractical. Explains tradeoffs and tool interactions (UBSan, sanitizers, static analysis).

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" chapters (42)

1. 0:00Introduction to safety
2. 2:37Understanding UB
3. 5:35How UB affects compilation
4. 6:43Concrete examples of UB
5. 10:10Mitigating UB risks
6. 12:12The trade-offs of safety
7. 14:20Language evolution strategies
8. 18:39Current safety proposals
9. 21:35Introduction to contracts
10. 23:53Narrow vs wide contracts
11. 26:12Analyzing Vector contracts
12. 28:46Soft vs hard UB
13. 31:28Implementing contract checks
14. 34:22Contract semantics
15. 36:44The 'assume' semantic
16. 37:43C++23 assume attribute
17. 39:56Assume in production
18. 42:51Assume benchmarks
19. 44:23Contract kinds
20. 46:22Testing postconditions
21. 48:45Class invariants
22. 50:09Contracts vs unit testing
23. 52:21Testing precondition checks
24. 55:09Exception-based testing
25. 57:05The noexcept conflict
26. 58:53The Lakers rule
27. 1:00:53Purpose of noexcept
28. 1:02:13Debating noexcept usage
29. 1:04:14Workarounds for testing
30. 1:06:13Death tests
31. 1:09:09Final recommendations
32. 1:12:31Noexcept code gen
33. 1:14:04Future of noexcept
34. 1:15:25Standardizing contracts
35. 1:17:18History of proposals
36. 1:19:20SG21 and the MVP
37. 1:21:18Contract MVP features
38. 1:23:32Build modes
39. 1:25:25Violation handler
40. 1:27:09Future contract applications
41. 1:29:38Contract syntax debate
42. 1:32:39Looking ahead

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